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Spermatogenesis in Ixodes 
i.e. the conjugation and the reduction of the chromosomes, have become 
special subjects for investigation and such researches are becoming increasingly 
specialized, because they demand specially adapted material and a great 
sacrifice of time. 
Owing to lack of opportunity for the complete elucidation of the various 
problems concerned in spermatogenesis, and the Ixodes material not being 
very suitable for the purposes of investigation, I shall deal summarily with 
certain aspects of the subject and confine myself here to tracing the changes 
that are undergone by the young spermatid whilst developing to the full- 
grown spermatozoon. 
The spermatogonium. Among the elements of the testis the spermato¬ 
gonium is, as usual, the smallest (PI. XI, fig. 1); its plasma is homogeneous, 
finely granular, without any distinct inclusions; its nucleus is relatively 
large, spherical, with a large nucleolus, a fine and close linin-network, and, 
scattered over this, a very finely granular chromatin. At the mitosis, this 
substance forms 28 short, slightly curved, rod-shaped chromosomes. The 
centrosome appears at the division as a very conspicuous, triangular corpuscle; 
but as will be shown, it is hard to follow its later development. The sperma- 
togonial divisions appear in the earlier part of the nymphal stage at a time 
when the whole gonad still forms a narrow tube with homogeneous contents. 
The later development of the gonad cells appears, on the other hand, only at 
the beginning of the last moult before the prosopon stage. 
The spermatocyte. The resting spermatocyte of the first order (PI. XI, 
fig. 2) shows a round or, when pressed by crowding, a somewhat angular 
shape. The globular nucleus forms the largest part of the cell. It shows a 
well-developed linin-network, on which the chromatin is scattered in the form 
of slender threads. The nucleolus is large and the nuclear membrane thin. 
The surrounding plasma has a double structure: the inner zone around the 
nucleus is uniformly fine-granular and contains larger or smaller aggregations 
of mitochondria. Around this inner zone is seen an outer layer, somewhat 
resembling a zona pellucida, and composed, as a closer investigation will show, 
of a denser and more deeply staining matrix, through which extends a 
system of diffuse less deeply staining processes from the inner plasma'. The 
resting spermatocyte of the second order differs from that of the first order 
only by its smaller size. 
The spermatid is, as usual, smaller than the spermatocytes. Beginning 
with the telophase of the second maturation division (PI. XI, fig. 3) there 
is seen, along with the redissolving chromosomes, the centrosome closely 
attached to the nucleus, often hidden among the chromosomes, and always 
as a matter of fact, opposite the spindle. The spermatid, when full grown 
(PI. XI, fig. 4), shows a nucleus with generally the same arrangement of 
chromatin and achromatin as in the spermatocytes, for it shows a reticular 
linin and, scattered in it, a granular chromatin; the nucleolus is conspicuous 
by its size, and is indeed far more voluminous than in the former cells. The 
