FECUNDATION OF THE NEMATOIDA. 307 



also, as in Mermis, cake together in lumps. At first we only see 

 the external outline of the rounded egg, sharper and darker, and 

 sometimes we may still detect the micropyle, which is frequently 

 furnished with a vesicle, the remains of the membrane of the deve- 

 lopment-cell ; the micropyle becomes closed by the thickening of 

 the envelopes, and we observe that a peculiar alteration commences 

 in the interior of the yelk. The germinal vesicle has by this 

 time disappeared ; at the periphery of the vitellus there are struc- 

 tures resembling fat-drops. According to Meissner, these are 

 the seminal corpuscles which have become converted into fat- 

 drops, which, however, according to Thompson, is by no means 

 proved, although he is not in a position to state what finally 

 becomes of the seminal corpuscles. Thompson — who is very well 

 acquainted with these clear, round or oval, strongly refracted 

 globules, which are apparently surrounded by a peculiar mem- 

 brane, but who could never detect their production from the 

 conversion of seminal corpuscles — regards them as an indication 

 of a change in the intimate constitution of the vitellus, which is 

 in itself connected with fecundation. These (fat) globules after- 

 wards fuse directly with the vitellus, which again changes its 

 chemical nature, and loses its emulsion- like condition. From 

 the vitelline granules which are particularly accumulated in the 

 middle of the egg, very clear, reddish, shining drops issue, and 

 attach themselves at its periphery like a wreath, and regularly, 

 close to the vitelline membrane ; processes which take place pretty 

 rapidly. This gives the egg a spotted appearance, and Nelson 

 calls it the spotted state of the vitellus. The vitelline granules 

 dissolve, and the contents of the yelk are a pale yellowish mass, 

 with a few larger and smaller granules, different from the previous 

 vitelline granules. During the same period the whole mass con- 

 stantly becomes more and moi'e condensed ; the periphery is 

 coated with homogeneous contents ; the yelk draws back from the 

 vitelline membrane, diminishes in volume almost one half, and 

 swims as a transparent mass in the interior. In this interval 

 the egg has passed down into the uterus, and become enveloped 

 b}' a chorion. At the same time small folds frequently appear 

 in the vitelline membrane, which assumes the contour of the 

 egg-envelopes. After this, a small clear space forms in 

 the middle of the yelk, surrounded by granules more densely 

 pressed together at its edges, and with the appearance of this 

 space (the first embryonal cell, according to Kolliker,) commences 



