380 E. R.-Dowxine, 
of Hydra, though their nature was not then recognized. The pro- 
jecting tubercles he considered abnormalities. In 1744 TREmMBLEY 
figured the male (79); so Rosen (73), SCHRANK and others observed 
and described the male organs but all considered them pathological 
structures or parasites. In 1836 EHRENBERG (18) described both the 
ee and sperm. Still LAURENT (58) writes in 1844 in regard to these 
pustules that he can not consider them analogous to testes, but 
with TREMBLEY and RÔSEL he regards these tumors as maladies 
and thinks the eggs develop without fecundation. (Voyage de la 
Bonite, Nouvelle Recherches sur ’Hydre, p. 20 and 40.) 
In 1872 KLEINENBERG (47) published his volume on Aydra. 
Regarding the spermatogenesis he says that the formation of the 
spermary begins by the rapid growth of the interstitial cells over 
a limited circular area. These divide rapidly a number of times, 
then become amoeboid. Ultimately they pack closely together and 
elongate. The nucleus then disintegrates while the cell substance 
becomes granular. There then appear in the cells, one to four 
strongly refractive oval bodies, whether formed from the disinte- 
erated nucleus or not he does not know. These refractive bodies 
become the nuclei of smaller cells from which the sperm form by 
the growth of the tail from one end. 
The results of BERGH and Korornerr (52) are very similar 
except they claim that the sperm are formed directly from the nuclei 
of the multinucleate sperm mother-cells. In 1885 Tearıwırz (80) 
published an investigation “Uber die Entwicklung der männlichen 
Keimzellen bei den Hydroiden”. He is the first to undertake to 
trace nuclear and cellular changes among hydroids during spermato- 
genesis. In the several which he investigated he says the course 
of spermatogenesis is somewhat as follows: — The primary spermato- 
blasts are derived from the ectoderm and are characterized by their 
reaction toward reagents, their sharp nuclear contour and their 
wealth of protoplasm. They multiply always mitotically, and emi- 
erate to the gonophore, where multiplication continues, until the 
sonophore is packed full. Then the protoplasm of the germ cells 
is lost so that the cell is little larger than the nucleus. The nucleus 
which heretofore has stained with difficulty now takes on a deep 
stain, while the nucleolus heretofore distinct disappears. Division 
follows and from the small cells formed the sperm are evolved, the 
nucleus becoming the head of the sperm. His points of advance 
are, then, the recognition of a series of complex nuclear changes 
