the thickened basement membrane by a stalk. A 

 few of the largest oocytes appear free in the lu- 

 mina of alveoli. Amphinucleoli prominent in the 

 largest oocytes. 



Ripe stage. Numerous large oocytes in the la- 

 mina of alveoli. Basement membrane thin, con- 

 taining only a few developing oocytes. Most 

 oocytes appear free in the lumina of alveoli. 



Partially spent stage. Some small oocytes em- 

 bedded in the basement membrane, with reduced 

 numbers of large oocytes in the alveoli lumina. 



Spent stage. A very few of the largest oocytes 

 in some of the alveoli lumina. Basement mem- 

 brane somewhat thickened and containing small 

 embedded oocvtes. 



earliest part of this stage. Secondary spermato- 

 cytes and spermatids proliferating into the cen- 

 ters of the lumina. Differentiated spermatozoa ar- 

 ranged in dense radiating bands at the centers of 

 the lumina. 



Ripe stage. Lumina of alveoli densely packed 

 with spermatozoa. Fewer spermatocytes and 

 spermatids occurring than in the preceding stage. 



Partially spent stage. Few to no spermato- 

 cytes or spermatids at the basement membrane. 

 Relatively reduced numbers of spermatozoa in 

 the lumina of alveoli compared to the ripe stage. 



Spent stage. Alveoli nearly empty of sperma- 

 tozoa, but a few near the basement membrane 

 and in the lumina. 



Males 



Early stage. Alveoli semicontracted, base- 

 ment membrane thickened, and follicle cells 

 prominent in the lumina. A few spermatogonia or 

 spermatocytes occur at the periphery of the lu- 

 mina in most clams, but some with a few sperma- 

 tozoa scattered in the lumina of some alveoli. 



Late stage. Alveoli expanded, basement 

 membrane thin and attached follicular cells less 

 apparent. Primary spermatocytes numerous at 

 the basement membrane, especially during the 



For all three sites, gametogenesis progressed 

 from the early to late stages from 21 February to 

 24 April 1974 (Table 3). Ripening was earliest at 

 Horseshoe Cove, with 109f of the clams in this 

 condition by 22 May and TO'/r by 19 June. At this 

 latter date, 509r of the Ward Point clams were 

 ripe. Clams at all the sites had ripened by 23 July, 

 and some (20'^f ) at Ward Point and many (70'';/ ) at 

 New Dorp Beach were in the partially spent con- 

 dition, an indication that spawning had begun at 

 these two sites. Spawning was later at Horseshoe 

 Cove, with 679^ in the partially spent condition by 

 21 August. Ripe clams were observed in the sam- 



Table 3^ — Percent occurrence of developmental stages during the reproductive cycle of Raritan 

 Bay hard clams, Mercenana mercenana. collected in 1974 and 1975. 



657 



