SPERMIOGENESIS OF HELIX ARBUSTORUM. 
325 
This depression becomes balanced by a casting of chromatin into the 
cytoplasm. The chromatin thus thrown forms the chromidia. 
This hypothesis may be supported by the fact that the chromidia 
first appear close to the nuclear membrane, and lie at the open ends 
of the loops. The connection is so regular that we must assume a 
nuclear origin of the chromidia, as it has been shown by E. Hertwig 
in Protozoa. It was observed by several authors that chromatin gets 
from the nucleus into the cytoplasm, for instance : Goldschmidt (32) 
observed the process in Ascaris , Mathews in the pancreas cells of 
Amphibia, Henschen (47) in ova of Helix pomatia, Stevens (115) in 
ovocytes of Sagitta , A. and K E. Schreiner (111) in spermatocytes of 
Myxine glutinosa , etc. Chromidia can be found in the cytoplasm also 
earlier, by which is shown that the suppression of the depression by 
the casting out of a part of the chromatin begins earlier, but the real 
formation of the chromidia only takes place after the suppressed division. 
This explanation has a difficulty, viz., it is difficult to understand 
the great capacity of the pachytene cell for absorbing chromidia which cell 
has such a small amount of cytoplasm. Such a depression is followed 
in Protozoa ; by conjugation, but in the life of the germ-cells we do 
not know a process like that, therefore we must either suppose that 
the cytoplasm even then has the capacity of absorbing as much chro¬ 
midia as is sufficient to improve the nucleo-plasmic ratio at least to 
such a degree that the increased assimilation can begin, or there must 
occur another process which gives the first impulse to surmount the 
depression. In the spermatocytes of H. arbustorum, as I believe, such 
a process occurs, but I shall discuss this question later. 
Goldschmidt (32), as is known, explained the origin of the chro¬ 
midia from the hypothesis that originally every nucleus (amphinucleus) 
has two kinds of chromatin, viz., idiochromatin and trophochromatin, 
the former representing the hereditary substance of the cell, the latter 
being the directive factor of the other functions of it. The tropho¬ 
chromatin, or parts of it, get during increased function into the 
cytoplasm, and form their chromidia. This process may be observed in 
every strongly functioning cell, but it is mostly evident in the germ-cells. 
It is undoubtedly true that Goldschmidt’s hypothesis has some disput¬ 
able points, but it is true as well that it gives — in connection with 
the hypothesis of depression of Hertwig — a useful key to the under¬ 
standing of some functions of the cell, viz., it makes understandable 
that the hereditary parts of the chromatin do not become annihilated 
when the chromatin of the nucleus after pachytene stage so strikingly 
diminishes. 
