ON THE DEVELOPMENT OF LINGULA ANATINA. 5 



mechanism of ovulation ; for the females, even when the sexual 

 product is actually ripe, will, when kept separate from the males, 

 fail to deposit eggs. Joubin ('86) also observed that on keeping 

 Crania the eggs atrophy, and turn into yellow bands (p. 255). 

 In order to test the above hypothesis an experiment was tried 

 last summer : several full grown males 1 were cut open and sperm 

 was taken into a glass vessel. It was then scattered by means 

 of a pipette around the females or injected in to the mantle 

 cavity of the latter. But unfortunately this did not produce any 

 result, owing perhaps to the fact that the female element was 

 not ripe enough. 



During the summer just past (1901) Lingida spawned twice 

 in captivity ; the first spawning took place early in the morning 

 of August 7th (23rd of the lunar calendar). The water had been 

 changed on the previous day after standing several days. Un- 

 fortunately I failed to observe the process of spawning and only 

 found fertilized eggs on the mud in which the specimens were 

 kept. In the second case the eggs discharged did not develop 

 at all owing perhaps to the fact that the water had already 

 become stagnant. From the above three cases I cannot find out 

 exactly what it is that induces spawning. Anyhow it is almost 

 certain that the spawning seems to take place under unfavorable, 

 rather than favorable, circumstances. 



In Lingula the breeding season is, in Misaki at least, very 

 short and certainly restricted to one month and a half of the 

 summer, i.e. from the middle of July to the end of August, as 



1. It has become not a very difficult matter to me to distinguish the sexes of Lingula 

 from without. As the shell is translucent, the female appears dark brown while the male 

 is of lighter brown colour or rather whitish. The distinction of colours between sexes is 

 most conspicuous in individuals of a medium size; for in older animals the shell increases 

 in thickness, so that light hardly passes through it. 



