OF THE GERMINAL LAYERS IN GASTROPODA. à 



becomes completely changed to dusky brown, owing to the pre- 

 sence of the shell. Besides the egg there is, within the chorion, 

 an abundant supply of albuminous material uniformly distributed 

 in the form of rather coarse spherules. Fig. 2 shows the general 

 view of the egg in the chorion, which is seen to be enveloped 

 in a thin layer of gelatine not yet coagulated. The spherules 

 just cited are homogenous and translucent ; but at about the time 

 of the expulsion of the second polar body, vacuoles are produced 

 in them (Fig. 3). Subsequently, all of the spherules gradually 

 disintegrate, leaving behind only very fine almost imperceptible 

 granules. They, however, can be easily coagulated, and therefore 

 may be brought into view by the application of hardening reagents. 

 By the time this coagulation stage is reached, it is found that 

 the distribution of the albuminous material is no longer uniform 

 throughout as was the case before disintegration. There is 

 almost always a smaller quantity towards the side, which is upper- 

 most in Fig. 4, i.e. the future dorso-anterior end of the egg, than 

 on the opposite side. 



JEffgs of Aplysia : — In tliis species too, the eggs are deposited 

 in a mass ; but here it is in the form of a very long and intricately 

 and loosely entangled cord which is about 1-1 è vim. in diameter. 

 In this cord there is recognizable, even with tlie naked eye an 

 innumerable number of yellow capsules, which are, as in the case 

 of the former species, connected by a thin thread and enveloped 

 in gelatine. The capsule represents the chorion, and enclosed 

 therein we find eggs usually more than thirty in number (Fig. 

 37, PI. II). The egg has a spherical contour, and is about 0.12 

 m7)i. in diameter. As is seen in Fig. 38 coarse granules of 

 deutoplasm are conspicuous in that part of the egg which becomes 

 the anterior portion of the future embryo. Their color is very 



