NOTES ON SOME OF THE EARLY STAGES OF DEVEL- 

 OPMENT OF THE CLAM OR MANANOSE (Mya 



arenaria.) 



The spawning period of this moUusk lasts from the 

 10th of September to about the middle of October, or for 

 about forty days. The sex of the adults, in a spawning 

 condition, maybe very easily learned. Open the shell 

 of the animal carefully, remove a small portion of the 

 richly colored yellow body mass with a knife, scissors or 

 forceps. These fragments, squeezed or "teased out" in 

 a watch-glass with a few drops of sea- water, allow a 

 milky fluid to escape. Under a magnifying power of 

 four or five times, the eggs of the female are visible in 

 this milky fluid as very minute white points of' nearly 

 uniform size. The male cells are too small to be seen 

 with the aid of so low a magnifying power, and the fluid 

 retains its milky apqearance just as it does to the naked 

 eye. It is only under high powers, as much as 250 dia- 

 meters, with the compound microscope, that the sper- 

 matozoa or male cells may be made visible, as minute 

 oval bodies with a long, lash-like tail in rapid motion. 

 These differences enable the operator to distinguish the 

 sexes, after a little experience ; indeed, it is possible 

 with training, to note the differences between the male 

 fluid and the eggs of the female when removed from the 

 animals, with the naked eye. 



Artificial impregnation of the eggs was effected in the 

 same way as in the case of the oyster ; that is, portions 

 of the ripe ovary of the female are removed and chopped 

 up in a watch-glass or small saucer with sea- water, taking 

 care to remove all the large fragments of ovarian tissue 

 by straining the milky substance through bolting cloth, 



