SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* Reiss Stan J (Last) (First) (Middle) C/O MATRIX PARTNERS VIII, L.P. 101 MAIN STREET, 17TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Acacia Communications, Inc. [ ACIA ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 05/15/2018
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/15/2018		J(1)		1,000,000	D	$0	8,646,247	I	By Matrix Partners VIII, L.P.(2)
Common Stock	05/15/2018		J(3)		551	D	$0	4,767	I	By Weston & Co. VIII LLC(4)
Common Stock	05/15/2018		J(3)		551	A	$0	5,380	I	By Matrix VIII US Management Co., L.L.C.(2)
Common Stock	05/15/2018		J(5)		300,082	A	$0	305,462	I	By Matrix VIII US Management Co., L.L.C.(2)
Common Stock	05/15/2018		J(6)		295,831	D	$0	9,631	I	By Matrix VIII US Management Co., L.L.C.(2)
Common Stock	05/15/2018		J(6)		2,505	A	$0	5,024	I	By The Reiss Family Irrevocable Trust(7)
Common Stock	05/15/2018		J(8)		19,541	A	$0	43,635	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents a pro-rata distribution, and not a purchase or sale, without additional consideration by Matrix Partners VIII, L.P. ("Matrix Partners VIII"), to its partners.

2. The shares are owned directly by Matrix Partners VIII. Matrix VIII US Management Co., L.L.C. ("Matrix VIII US Management Co."), which is the General Partner of Matrix Partners VIII and disclaims beneficial ownership of the shares owned by Matrix Partners VIII except to its proportionate pecuniary interest therein. Mr. Reiss, a member of the Board of Directors of the Issuer and a managing member of Matrix VIII US Management Co. has sole voting and dispositive power with respect to these shares. Mr. Reiss disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.

3. Re-registration of shares by Weston & Co. VIII LLC ("Weston VIII"), without consideration, in the name of Matrix VIII US Management Co., the beneficial owner of those shares.

4. Matrix VIII US Management Co. is the beneficial owner of the shares reported herein as being held of record by Weston VIII, and disclaims beneficial ownership of the shares owned by Weston VIII except to its proportionate pecuniary interest therein. Mr. Reiss, a member of the Board of Directors of the Issuer and a managing member of Matrix VIII US Management Co. has sole voting and dispositive power with respect to these shares. Mr. Reiss disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein.

5. Represents the shares received in connection with the pro-rata distribution by Matrix Partners VIII, without consideration to its partners.

6. Represents pro-rata distribution by Matrix VIII US Management Co., without consideration, to its members.

7. Shares held by The Reiss Family Irrevocable Trust. The reporting person is a trustee and beneficiary of the trust.

8. Represents the shares received in connection with the pro rata distributions by Matrix Partners VIII and Matrix VIII US Management, Co., each without consideration, as described in this Form 4.

Remarks:

	/s/ Stan J. Reiss	05/17/2018
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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