‘ioe 
ON THE REPRODUCTIVE SYSTEM IN THE HYDROIDA. 405 
Fig. 20.—Development of the ovum in Laomedea flewuosa. 
ey SEF. ie 
A, young ovum in the gonophore previously to the disappearance of the germinal vesi- 
cle: the germinal vesicle is here seen to contain several germinal spots ; B, the germinal 
vesicle and spots have disappeared ; C, the vitellus has become cleft into two segmenta- 
tion-spheres ; D, the ovum after the second cleavage; E, the segmentation-spheres have 
become numerous, and many of them now show a distinct nucleus; F, the segmentation- 
spheres have greatly increased in number, and a nucleus may now be detected in each of 
them ; G, the most superficial spheres have become arranged into a stratum distinguish- 
able from the deeper portion of the ovum; H, the superficial stratum has become more 
distinct, and is now seen to be composed of long prismatic cells ; I, the ovum has begun to 
elongate itself, and one end has become folded on the remainder ; K, the embryo just after 
its escape in the form of a ciliated planula. 
