296 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
y. Gastropoda. 
Spermatogenesis of Snail.* * * § — Hr. A. Bolles Lee lias made a detailed 
study of the spermatogenesis in Helix pomatia. The basal cells — the 
male ovules of Duval, the blastophoral cells of Blomfield — do not produce 
the spermatogenetic cells which they bear ; in fact they are wholly sup- 
porting and nutritive elements. The spermatogenesis concerns three 
categories of cells, the spermatogonia and two sets of spermatocytes. 
In the kinesis of the spermatogonia, there is a peculiar phase with scat- 
tered nuclear segment — la phase cle V eparpillement — intercalated between 
the stage of regular corolla-like distribution (de peloton secjmenle) and 
the equatorial corona. It is possible that there is in this intercalated 
phase a qualitative reducing division. 
The kinesis of the first set of spermatocytes resembles the kinesis 
a batonnets droits of Carnoy, the heterotypic division of Flemming, the 
essential feature being that the segments resulting from the longitudinal 
splitting of a primary nuclear segment fuse into a single chromosome. 
Thereafter ensues a resting stage, followed by the kinesis of the second 
set of spermatocytes in which there is a qualitative and quantitative, but 
not a numerical reduction. Indeed, there is no numerical reduction 
throughout the whole process. What various authorities call centrosomes 
are really “ siderophilous corpuscles ” produced by and expelled from the 
nuclei, but quite devoid of any mechanical role in kinesis. Both karyo- 
plasm and cytoplasm show a reticular structure. The cytoplasm is not 
centered in relation to a centrosome, and has no “ organic radii ” nor 
“ attraction spheres.” 
Repeated Bipolar Mitoses in Mother-Sperm-Cells of Snail. f — Herr 
E. Godlewski, jun., finds evidence of 2, 4, 8, and perhaps more bipolar 
mitoses in one cell. Sixteen spermatozoa may thus arise from one 
mother-cell. Unlike Bolles Lee, he always finds centrosomes at the 
spindle-poles. The details of the change from spermatid to spermato- 
zoon are given, and the author substantiates the generally accepted view 
that the centrosome enters into the middle portion of the sperm. 
Asymmetry of Gastropods.! — Prof. H. Simroth concludes that the 
oldest molluscs had paired copulatory organs, corresponding to the 
jirimitively paired disposition of the gonads and nephridial ducts. But 
the increase of sedentary habits, on rocks (where the shell arose) and in 
the mud (Scaphopods and bivalves), led to the disappearance of copula- 
tory organs. The mobile Cephalopods retained them, on both sides 
or on one. The Gastropods kept them or re-acquired them on one 
side only. It seems to Simroth that the evolution of the asymmetry of 
the Gastropods is wrapped up with the history of the copulatory appa- 
ratus. A review of other theories is given. 
Connective Tissue of Paludina.§ — M. Joannes Chatin has studied 
the behaviour of the connective tissue elements in Paludina vivipara , 
when this mollusc is affected with Cercariae. The general result of his 
* La Cellule, xiii. (1897) pp. 199-27S (3 pis.). 
t Anzeig. Akad. Wiss. Krakau, 1897, pp. 68-81 (2 pis.), pp. 263-7 (3 figs.) See 
Zool. Centralbl., iv. (1897) pp. 880-3. 
% Biol. Centralbl., xviii. (1898) pp. 54-63. 
§ Comptes Kendus, cxxvi. (1898) pp. 659-62. 
