THE DEVELOPMENT OF THE SPERMATOZOA. 4.27 
vary in shape and arrangement, which he considers indica- 
tive of division and multiplication. Nearer still to the 
lumen of the tube the cells are loosely connected, and they 
may be seen dividing each into two daughter nuclei. These 
small cells, the daughter cells, undergo changes leading to 
the formation of the spermatozoa, and for these he uses 
Sertoli’s term spermatoblasts. The first change is seen in 
the nucleus, which becomes finely granular and assumes a 
membrane. This kind of nucleus he calls the resting 
nucleus. At the same time it moves to one pole of the 
cell, which is itself elongated, and constitutes a “ granular 
mass,” separated from the nucleus by a “ clear bag.” When 
the young spermatozoa are in this state they assume a defi- 
nite arrangement, and become placed in fan-shaped groups 
along the tubule, with the handle of the fan sunk among 
the seminal cells; their further progress consists in elonga- 
tion. He then goes on to mention the views of Ebner and 
Neumann, who consider that the groups of spermatozoa are 
formed in a single cell which consists of a base, which has 
(Ebner) or has not (Neumann) a nucleus next the membrana 
propria, a peduncle, and a broad mass at the end of the 
peduncle in which the spermatozoa are produced. 
He regards the head, as well as the “ middle piece,” as 
formed from the nucleus. 
In Rollett’s ‘ Untersuchungen aus dem Institut fur Phys. 
und Hist.’ for 1871, there is a paper by v. Ebner, in which 
he gives an account of the development of the spermatozoa 
in the rat and mouse, referring to other mammals, and a 
series of drawings illustrating that process in the first-named 
animal. 
He divides the processes into eight stages, which I will 
not enumerate, but try to epitomize his account. The funda- 
mental idea in which he differs from other writers is in the 
existence of a “ Keimnetz,” in which the spermatozoa are 
developed. This consists of a welded mass of cells next the 
tunica propria of the tubule in which two kinds of nuclei are 
discerned, the one pale, nucleolated, with distinct outline; the 
other granular, dark, with anindistinct outline. On taking a 
* superficial view of this layer it has the appearance of a net- 
work. From it processes project towards the lumen of the tu- 
bule which, when first formed, are nothing but plasma; then 
nuclear hardenings commence at its inner extremity, which 
soon unmistakably assume the appearance of spermatozoa 
heads, in this case being pointed at one end, which end is 
directed towards the periphery. The tails are formed from 
the plasma. At the base of this process, which he calls a 
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