88 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
number of half chromosomes or one fourth the original chromatin 
mass. 
38. With reference to the number of chromosomes, the second 
maturation division is the reducing division. 
39. There are two kinds of spermatocytes as there appear to be 
two kinds of primary spermatogonia, and, as we shall see, two kinds 
of spermatids. 
40. From the above facts, and also from the sorting of the chromo¬ 
somes in the last maturation division, it must be inferred that, even 
if the chromosomes are bearers of heredity, in Weismann’s sense, 
the spermatids and consequently also the mature spermatozoa differ 
in their hereditary qualities. 
41. The equal division of the cytoplasm is as scrupulously accom¬ 
plished here as is the equal division of the nucleus. 
42. The theory of the individuality of the chromosomes is well 
sustained here. 
43. There are reasons for believing that the fibers of the spindle 
are capable of being split up into smaller fibrils, and that these thin 
fibrils can reunite into larger fibers. 
44. The theory of a special archoplasm giving rise to the astral 
rays is not at all sustained here. 
The Spermatid. 
As there are giant spermatogonia (stalked cells), and giant sperma¬ 
tocytes, so there are giant spermatids. Excepting their size, there is 
nothing to show that these giant spermatids are abnormal or patho¬ 
logical. I am convinced that their unusual size is not due to an 
arrested mitosis during maturation. Degenerating gonocysts have 
already been noted. The spermatogonia they contain often differ 
in size as three or four to one. As the largest of these may contain 
two or even four nuclei (pi. 13, fig. 33), I feel safe in assuming that 
they are cases of arrested mitosis. Their variable degrees of disin¬ 
tegration in the same cyst or in different cysts are sufficient evidence 
of their pathological condition. 
There are, however, also spermatocytes with tw T o or even three 
nuclei (pi. 17, figs. 122, 123). All these nuclei are well developed 
and evidently as normal as those where only one exists. The cyto- 
