The spermatogenesis of Hydra. 385 
swimming in the contained fluid. The activity of the sperm is very 
ereat, so that it gives to the fluid in the tip the appearance of 
boiling. Within the basal part of the spermary lines of yellowish 
brown granules may be seen extending up into the otherwise color- 
less testes among the rapidly dividing cells. These are found in 
sections to be nutritive material, and their fate will be discussed 
later. 
Rupture of the spermary. 
When the spermary is well distended with active sperm, the 
tip ruptures and the sperm are set free. After the rupture of the 
spermary and the discharge of its sperm there still remain many 
interstitial cells and some of the spermatocytes and spermatogonia. 
Some of these continue to divide and form spermatids and so sperma- 
tozoa, but there soon ensues among them a degeneration. 
Phagacytosis. 
Giant multinucleate cells, possibly phagocytes, are formed, 
apparently by the fusion of adjacent cells. The outer thin lamella- 
like portions of the ectoderm cells slough off. The giant cells seem 
to be slowly resolved; at least they disappear by some process; the 
elongated ectoderm cells resume their normal proportions, and thus 
the tissue regains its normal appearance. 
Adult spermary. 
The adult spermary varies greatly in size. Section through a 
Hydra in the plane of an average sized testis is given in Fig. 11. 
The dimensions are as follows: 
Height of spermary along the dotted line, 122.0 u 
Diam. of base 8 1 2230% 
Thickness of ectoderm „ i = La 
5 „ endoderm „ 4 r 94.0 „ 
Diam. of body cavity „ x ST LOLS 
When the spermary is well matured a section through it gives 
a figure like Fig. 9. The very elongate ectoderm cells form support- 
ing strands, their outer plate like ends forming the outer wall of 
the spermary. The basal part of the spermary is occupied by the 
spermatogonia. The other cell generations are to be noted more 
peripherally, usually in no well defined order. The peripheral por- 
tion is occupied by sperm free swimming in a fluid. This is pro- 
bably nutritive in nature, for with fixing agents it forms considerable 
coagulum. 
