SPERMIOGENESIS OF HELIX ARBUSTORUM. 
315 
differs, however, from it, since the chromatin of the spermatogonia and 
spermatocytes forms a united thread, on the contrary in the second 
spermatocytes more or less isolated chromatin masses are to be found, 
i. e. the chromatin does not form a reticulum. The secondary sperma¬ 
tocytes of H. pomatia, according to Bolles Lee (10) and Prowazek (98) 
always go through this stage, but Bolles Lee emphasized the fact that 
though between the two maturation divisions a resting period is inter¬ 
calated which is succeeded by a normal prophase, this resting period 
is, in comparison with the corresponding period of the ordinary division, 
reduced, being so to say its extract. According to Tschassownikow (120) 
the first maturation division in H. pomatia always is succeeded by a 
definite, perfect resting period. 
There is no doubt that we must regard this as the ordinary man¬ 
ner of maturation divisions in which a shorter or longer resting period 
is intercalated between them, and the one first mentioned is only an 
exception which can be concluded from the rarity of the microscopical 
figures showing it. But several animals and plants are known, the reduc¬ 
tion divisions of which take place in the manner which is in H. arbu¬ 
storum exceptional. In several plants, as I know from Grégoire’ s 
paper (37) the second maturation division immediately succeeds the 
first ( Convallaria : Schniewind-Thies, Tricyrtis : Ikeda, Pallavicinia : 
Farmer, Moore). But, as a rule, the plants also have a tendancy to go 
before the second division into a short resting stage. Similar cases are 
known also in animals. Platner (93) observed that the second matura¬ 
tion spindle can form before the cell has arrived at the anaphase. 
According to vom Bath (99) in spermatogenesis of Gryllotalpa the 
second maturation division immediately follows the first without the 
nucleus being transformed into a resting nucleus. At other times, though 
a nuclear membrane arises, the nucleus does not become a resting 
nucleus, since the chromosomes preserve their independence {Ascaris: 
Brauer). Again in other cases a definite resting period separates the 
maturation divisions (rat: Lenhossék, Ebner; Scolopendra : Blackman; 
Gonionemus : Bigelow, etc., etc.). Bolles Lee (10) tried to refute Plat- 
ner’s and vom Bath’s statements, but my observation made in H. ar¬ 
bustorum shows that the second maturation spindle can form before 
the cell reaches the telophase. 
The first phases of the division of the second spermatocytes in 
the case when it was preceded by a resting period, I have not had 
the opportunity of observing. According to Bolles Lee (10) the outlines 
of the chromosomes of H. pomatia preparing to division become shar¬ 
per and smooth, and then more chromatic than formerly. In a slightly 
