20G REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
Since the peculiar cells of Fig. 27 are signs of division they are not 
always present, but in some tubes they are absent altogether. The mul- 
tiplication of the spermatoblasts by self-division is interesting because 
it shows that all the male elements do not arise directly from the mother 
nucleus, a fact of most profound theoretical meaning. 
We must now pass to the consideration of the alterations of form which 
the spermatoblasts undergo after their multiplication ceases. As before 
stated, these changes occur altogether in the second segment of the 
tube. The body of the spermatoblasts begins to change before the 
nucleus, as is frequently the case with other animals, 287 and is perhaps 
even the general rule. In the grasshopper the cells begin to elongate, 
the nucleus remaining in the upper part. There remains a small head of 
protoplasm around the nucleus, while the rest of the protoplasm length- 
ens out to form a long tail, so that when the spermatozoon is about half- 
developed it consists of a head with a small, spherical, granulated nucleus 
surrounded by a little protoplasm, which is prolonged into a thread-like- 
tail. The further metamorphosis consists mainly in the elongation of 
the nucleus, it first becoming pointed at both ends and bulging in the 
middle, then growing more and more rod-like until it is quite filamen- 
tous and about six times its original length; meanwhile the protoplasm 
around the nucleus gradually disappears, forming probably the little 
thread that extends beyond the nucleus, and also contributing to the 
growth of the tail. The nucleus, while lengthening out, does not remain 
perfectly straight, but at a certain period of its formation is curved 
somewhat in the form of an S. The nuclei afterwards straighten out 
agaiu forming the heads of the spermatozoa and they then lay them- 
selves parallel to one another, and as they become more perfectly packed 
together they form the sharp-pointed bundles, which are so character* 
istic of the lower part of the second segment of the seminiferous tubes, 
Fig. 23, II. In a transverse section through the head of a bundle of 
spermatozoa, the heads appear as minute dots closely crowded together, 
while in a section of a younger bundle, Fig. 30, they lie at some distance 
apart. 258 
There now remain to be mentioned the very singular nuclei which 
appear in the walls of the seminiferous tubes in the lower three-quarters 
of their length. They are irregularly distributed, oval, very much flat- 
tened, quite large, and contain a few large granules, which alone are 
stained by hsematoxiline, the intervening space remaining perfectly clear. 
287 La Valletta St. George: Der Hoden in Strieker's Handbuch i, p. 522, especially figs. 183, 188, 189. 
TJeber die Genese der Samenkbrper. 4. Hittheilung. Arch, ilikros. Anat., Bd. xii, p. 797. 
Spengel: L c. 
Braun: Das Urogenital System der einheimischen Reptilien. Semper's Arbeiten, iv, p. 113. Hoden, 
p. 158 ff. 
KMlikcr: Handbuch der Gewebelehre, 5 Aufl., 1867, pp. 526-528. 
Sertoli: Sulla Struthora delli Canalicoli seminiferi, etc. Archivio delle Scienze Mediche, vol. ii, p. 
107 (1877). 
288 For other accounts of the development of spermatozoa in insects the reader is referred to H Meyer, 
Zeit. Wiss. Zool., Bd. i, p. 187. 
