at beginning of spawning is given as 10° to 12* Co Size of larvae is given 

 as 10 5 microns, earliest straight-hinge stage to 2$0 microns, metamorphosing 

 larvae. Good photomicrographs are presented. 



Wells (1927) and Loosanoff (unpublished) also give good photomicro- 

 graphs of Mya larvae of various sizes from early straights to metamorphosed 

 individuals . 



Turner (I9U8) states that the length of larval life varies with the 

 temperature of the water, warmer water favoring more rapid development. 

 The period may be as short as 12 days in Massachusetts and as long as 3 

 weeks in Maine. 



Deevey (19U9) says the Mya veligers are the dominant bivalve larvae in 

 Tisbury Great Pond, Mass., from late April into June and are present through- 

 out the summer. 



Venus .—Bel ding (1931) gives the spawning season of Venus in Massachusetts 

 waters as the middle of June to the middle of August. The water tempera- 

 ture at Wellfleet, where most of the work was done, at the beginning of 

 spawning was 76° F., and the duration of the free-swimming stage was 6 to 12 

 days. 



Kerswilli' says that in Bideford River, Prince Edward Island, in 1938, 

 1939, and 19ii0, spawning did not begin until the water temperature reached 

 23° C. Spawning continued until about September 1 as a gradual process. 



Deevey (19U9) states that Venus larvae were present in Tisbury Great 

 Pond in June, July, and August and are the dominant bivalve larvae in late 

 July and early August. 



Loosanoff (1937) and Loosanoff and Davis (1950j 195l) , and Loosanoff, 

 Miller and Smith (19^1) give much information on the physiology of Venus 

 larvae. They note that unprovoked spawning will take place at temperatures 

 as low as 20.6°C. This is lower than hitherto recorded in the literature. 

 The range of larval sizes is given as 10 5 microns ^ earliest straight-hinge 

 stage, to 227 microns, ready-to-set larvae. 



Wells (1927) and Loosanoff and Davis (195>0) have published photomicro- 

 graphs of Venus larvae of various sizes and ages. Those of Loosanoff and 

 Davis are particularly helpful for identification purposes because they 

 represent a greater variety of sizes and ages and are accompanied by a sup- 

 plementary description of changes in appearance with age. 



1/ Kerswill, C. J. 19Ul. Some environmental factors limiting growth and 

 distribution of the quahaug, Venus mercenaria . Doctoral Thesis, Univ. 

 of Toronto. 



