DEVELOPMENT OF THE SPERMATOZOA. 
205 
Let us now return to the examination of an isolated tube. In it also 
we can recognize the single cysts, and we perceive at once that each cyst 
pursues its independeut development, and gradually changes into one of 
the bundles that appear so very plainly in the second segment, Fig. 25 II. 
It will next be noticed that the further we descend the more numerous 
and the smaller the spermatoblasts in each cyst, the nucleus diminish- 
ing in size with especial rapidity. The nature of these changes appears 
in Figs. 26, 28, 29. Fig. 26 represents a few spermatoblasts from the 
upper portion of segment I; their characters have been already de- 
scribed. Fig. 28 is taken from lower down. Fig. 29 is taken from a 
transverse section of one of the upper bundles of the second segment. 
The cells have begun to lengthen, but the nuclei have not changed much. 
To this fact I shall recur directly. 
Segments I and II, Fig. 25, correspond to two natural stages in the 
development of the spermatozoa; first, the multiplication of the sperm- 
atoblasts; second, the metamorphosis of the spermatoblasts into the 
spermatic threads (Samenfaden). It is therefore only in the first seg- 
ment that we find the signs of division, which have been frequently 
noticed in the development of the male products in various animals (I 
may mention the Batrachians in particular 285 ), but have, I believe, hith- 
erto puzzled all naturalists, without exception. These signs of division 
are the cells, such as are shown in Fig. 27, which, instead of the ordinary 
nuclei, contain a number of very dark and very large granules, often 
somewhat irregularly distributed. I have been so fortunate as to obtain 
some of these cells isolated, and saw at once that they were in process 
of division, and upon closer examination, with a very high power (Tolle's 
immersion -r 2 th), I was able to see that many of them were in the condi- 
tion indicated by Fig. 27 A, elongated, constricted in the middle, the 
granules accumulated at the two opposite poles, and running between 
the two accumulations a faint striation. There can be no doubt that 
this represents the last stage of the division of the nuclei, by the forma- 
tion of a Kernspindel, that remarkable phenomenon which has been so 
actively studied in Germany and Switzerland during the last two years 
by so many distinguished observers. 286 This discovery naturally leads to 
a variety of theoretical considerations, which cannot be appropriately 
introduced here. I will add that I have observed several other stages in 
the formation of the Kernspindel, but as my investigations on this point 
are still incomplete, I will reserve further details for another occasion. 
^Spengel: Urogenital System der Amphibien. Semper's Arbeiten, iii, p. 1, plate ii, figs. 27-34, 
Spermatozoa of Epicrinm glutinosum. 
^BiiUchli: Studien iiber die ersten Entwickelungsvorgange der Eizelle, etc. Senkberg. Natf. Ges., 
Frankfort, Bd. x, p. 1. 
Zur Kenntniss der Theilungsprooess der Knorpelzellen. Zeitsch. Wiss. Zool., xxix, p. 206. 
Entwickelungsgeschichtliche Beitrage. Zur Kenntniss der Furchungsprocess bei Neplielis. 
Z. Z. xxix, p, 239. 
O. Hertwig: Befrachtung, etc. Morph. Jahrb. i, p. 347 ; iii, p. 1 and p. 271. 
H. Fol: Sur le Developpement des Pteropodes. Arch. Zool. Expt. G6n. (1875), Tome iii, p. 104 ; also, 
same journal, T. V, Fasc. ii. 
Compare also the writings of Auerbach, Strassburger, Balfour, et al. 
