SPERMIOGENESIS OF HELIX ARBUSTORUM. 
335 
As regards the structure of the axial filament I refer to Figs. 12. 
and 16., Pl. XI. The proximale centriole is, as is shown on Fig. 12., 
a flat disc the centre of which is perforated by a delicate fibril. This 
latter is, so to say, the axis of the axial filament which enters with its 
anterior end into the head. The part of the fibril between the proximale 
and distale centrioles is covered by a sheath the diameter of which is 
equal to that of the proximale centriole (Fig. 12.), therefore the axial 
filament consists of two parts : of an inner axis and an outer sheath. 
The true thicknes of the axis is to be seen on the part passing 
through the centrosome and having no sheath (Fig. 12). On prepara¬ 
tions, as a rule, either the axis alone, or the outer cover is to be 
seen, according to the degree of the washing out, and the change 
in the thickness of the axial filament is to be explained by this circum¬ 
stance. Successful preparations show, however, both parts. Both parts 
of the axial filament of the spermatozoa of Helix have only been seen 
till the present time by Bolles Lee (12). The axial filament consists, 
according to him, of an inner part (endostyle) and an outer sheath 
(exolemme) .From this latter only an inner riband-like part takes up the 
dyes which same part runs in a spiral line around the axis. The spiral 
line of the spermatozoa of H. pomatia is homologous with the outer 
sheath of the axial filament of H. arbustorum , and both arise from the 
mitochondria granules as well as the substance of the nebenkern. 
Similar process has been observed by Meves (72) in Paludina , by 
Benda and the present author (113 a) in Planorbis. The mitochondria, 
however, as is well known, give rise to spiral structures not only in 
Molluscs, but also in other animals, especially in Vertebrates. 
EXPLANATION OF PLATES. 
All drawings were made by Abbe’s camera lucida, and except Fig. 1. PI. I., 
with number 12 compensating ocular (Beichert), and P55 mm apochromatic ob¬ 
jective, apert. 1*35 (Beichert), length of the tube 160 mm. PI. I., Fig. 1. was made 
with number 6 compensating ocular and objective No. 9. (Beichert). 
PLATE VII. 
Fig. 1. Young acinus of the genital gland. Mayer’s picric-nitric acid, Hei- 
denhain’s iron-hematoxylin. 
Fig 2. Besting spermatogonia in a common ground plasm. Bouin’s picric- 
formol, Heidenhain’s iron-hematoxylin, preceded by anilin blue. 
Fig. 3. Spermatogonium, spireme. Perényi’s fluid, Benda’s natrium sulphaliza- 
rinate-toluidin blue. 
