284 J. E. S. MOORE. 
of the first spermatogenetic period, and in the course of this 
the features which appear to be of primary comparative im- 
portance may be summarised as follows : 
I. The existence in the resting cells of a large round nucle- 
olus lying near the nuclear periphery. 
II. The evolution during the prophasis of division, of twenty- 
four bent chromosomes, which shorten up, and split longitu- 
dinally in half to form the same number of chromosomes, 
twenty-four, in each daughter-cell. 
III. The existence of an extra-nuclear attraction sphere, 
which, during this period of the spermatogenesis, is practically 
destitute of archoplasm, being surrounded by a simple cyto- 
plasmic radiation like that observed in many forms of tissue 
cells. 
IV. The consequent non-formation of an archoplasmic spindle 
figure, and the dual origin of this latter structure, partly from 
the simple cytoplasmic radiation, partly from the intra-nuclear 
substance. 
V. The differentiation of the spindle during the dyastral 
figure into an outer and an inner fibrous sheath, which, after 
the escape of the parental nuclear sap, collapse and coalesce, 
forming a delicate connecting thread between the attraction 
spheres of both daughter-cells. 
VI. The formation of extra-nuclear chromatic bodies from 
the débris of the nuclear chromatin. 
IV. The Rest of Transformation (Synaptic Phase) 
between the First and Second Spermatogenetic 
Periods. 
19. As I have already pointed out, the transition from the 
first into the second spermatogenetic period is completed in 
the cells during the rest which follows the last division of the 
first, and when the elements in the ampullee are seven or eight 
rows deep (fig. 34). Such cells, although at first retaining the 
characteristics of those of previous generations, gradually acquire 
new ones, but so gradually that itis some time before we realise 
the profound nature of the changes wrought, and that, while yet 
