SPERMIOGENESIS OF HELIX ARBUSTORUM. 
323 
This explanation agrees with that given by Brauer (17) of the 
reduction of Ascaris megalocephala. 
* 
The growth period of the spermatocytes of H. arbustorum can 
be divided into two parts characterized by the processes which take 
place during transformation of the cytoplasm, and chiefly by those taking 
place during transformation of the chromosomes. The first part lasts 
till the formation of the bouquet, the second begins when the chromo¬ 
somes become scattered through the nucleus. The cell increases during 
the first part in a less degree ; the increase is limited almost to the 
nucleus, but the real increase takes place during the second part of the 
growth period. The chromatin is divided first into chromomeres suspen¬ 
ded in the linin network which gradually unite, to form thin threads. 
The thread divides afterwards into thicker, U-shaped, split chromoso¬ 
mes. The development of the chromatin agrees till that stage with that 
of the chromosomes of the somatic cells. The splitting of the chromo¬ 
somes is followed, as a rule, by the formation of the spindle and the 
division itself, and variation can be found only in the duration of the 
time during which the thread-like chromosomes transform themselves 
into the rod-shaped, ovoidal, or spherical chromosomes of the spindle. 
The development of the chromosomes of the spermatocytes of H. ar¬ 
bustorum differs from this scheme, since they do not transform them¬ 
selves after splitting into the definite chromosomes of the spindle, but 
lose their independence, and dissolve into chromomeres which become 
equally scattered through the linin network developed in the mean-time. 
The constitution of the nucleus in this stage is very similar to 
that of the resting spermatocytes, and thus we may say that the nu¬ 
cleus became again a resting one without preceding division, used the 
term «resting» in morphological, and not in physiological sense. 
Similar phenomena have also been observed by former authors, 
but chiefly in ovogenesis. According to Winiwarter (128) in ovogenesis 
of Mammals (man and rabbit) the same two periods are to be distin¬ 
guished as in spermatogenesis ol H. arbustorum. Two similar, but not so 
sharply determined parts are to be observed in ovogenesis of Amphibia 
(Carnoy and Lebrun), Triton (Lubosch), and Selachii. Amongst Inver¬ 
tebrates Schokaert (108) in Polyclctda (Thysanozoon Brocchii), Bonnevie 
(13, 14) in Enteroxenos, Stschelkanowzew (118) in Aphis, Goldschmidt 
(34) in Dicrocoelium lanceatum, Woltereck (129) and ScHLEip(107)in Oslra- 
coda (the latter author in Notodromas monacha and Cypris ovum), Popoff 
(94) in Taludina observed an intercalated resting stage (all these authors 
21 * 
