Desor on the Embryology of Nemertes. 3 
case the sphere is generally larger. Lastly some were found 
at the extremity of the string containing no yolk at all, but 
merely a transparent liquid. When crowded together, the 
yolks, which by themselves are spherical, become flattened at 
the points of contact, showing that they are of a soft consist- 
"ence. The transparent liquid, with which the yolks are sur- 
rounded, is similar to that found in the eggs of molluscous 
animals, which is commonly called albumen, from its similarity 
to the white of eggs in higher animals. But physiologically 
speaking, it is in neither case a true albumen, though it may 
contain albuminous matter. It is nothing more rior less than 
the mother liquid, so to speak, which becomes transparent as 
the vitelline matter condenses, and which I propose to call 
biogen liquid, in consequence of its great importance in 
embryology.’ 
The germinative vesicle and germinative dot, which are so 
distinct in the ovarian egg,” have completely disappeared after 
its extrusion, at least I never was able to discern it after the 
egg had been laid ; in place of it, we find in each yolk-sphere 
one or several clear or semi-transparent spots, not having a 
well defined outline, and which have been described by 
embryologists under the name of oil-drops, or clear dots. 
(Fig. 3-13.) 
1 See Proceedings of the Boston Soc. Nat. Hist. 5th July, 1848 
? See Johnston, Miscellanea Zoólogica, in the Magazine of Zoology and Botany, 
Vol. I. Pl. 17, Fig. 2 and 6. According to Johnston, the eggs are found in little 
masses on each side «c: the alimenfary canal. 
3 Considering the different opinions as to the nature and object of these spots, I 
bave devoted myself with great care to their examination, hoping that they might 
throw some light on this difficult question. "The following are the results of my 
observations. : 
On compressing the flasks, there are seen on the Pca. of the vitelline spheres 
little transparent vesicles like hernia. (Fig.4aand5a.) Considering their sharp 
outlines I was tempted at first to consider them as vesicles, but seeing that t on 
liquid, which, from the cohesion ofi its particles; took these well defined forms, as we 
see ina drop of oil. Ina p pon another mass of eggs, lob- 
