HARDWICKE'S SCIENCE-GOSSIP. 



157 



The shell is not smooth, nor is it covered with an 

 irregular network, as in H. viridis, but it is sur- 

 rounded with a transparent gelatinous envelope, 

 which it retains to the time of hatching. The egg 

 of H. viridis has at first also an envelope, which dis- 

 appears some time before hatching. In fig. 100, c, I 

 have particularly marked the triangular-shaped 



\: 





Fig. 102. F, part of the Hydra protruding from the egg. 



darker spots in the envelope; they appeared as 

 regular as in the sketch a little denser than the rest 

 of the envelope, and surrounding the whole of the 

 egg. This, however, can only be seen at the margin ; 

 but on moving the egg in the water, it may be seen 

 on every part, and always presenting the same 

 appearance. The diameter of the egg of H. vulgaris 

 is one-fiftieth of an inch, that of H. viridis one- 

 sixty-sixth of an inch. 



«-. 





Fig. 103. G, indication of tentacles. 



On October 27th, 1873, I placed in a glass cell a 

 specimen of H. vulgaris, on which an ovum had 

 begun to form. It was put into pure clean water 

 by itself, so that nothing obstructed the view, 

 and the changes which took place from time to 

 time were very clearly observed. Besides the 

 ovum it had three fully- developed sperm - cells 



(fig. 10G, K), in which spermatozoa were seen in 

 active motion, and from each of which,"at interval 

 a quantity was discharged into the surrounding 

 water (fig. 106, L) * 



Fig. 104. H, further development of tentacles. 





>~j- 



Fig. 105. Full development of young Hydra, fixed to the 

 inside of shell at /. 



* The spermatozoa were originally made out by Mr. 

 Gulliver, F.R S., who obtained specimens of the Hydra from 

 me, and executed drawings of the spermatozoa, which are 

 engraved in Science-Gossip, vol. for 18/~3, pages I3]and 41, 

 and are the first representations published of these objects in 

 this country, if not in the world. My own objectives were 

 not of sufficient power for such delicate investigations,, but 

 Mr. Gulliver, with Powell & Lealand's one-sixteenth, _was 

 well prepared. 



