STUDIES ON THE TURBELLARIA. 439 
In connection with the subject of the spermatozoa it may 
be worth while to mention that a remarkable micro-organism, 
presumably a Schizomycete, which is extremely common as a 
parasite of Heterocherus, particularly in the winter and 
spring, bears a very considerable resemblance to a spermato- 
zoon both in form and movements. It occurs in the interior 
of vesicles which are apparently degenerating cells, sometimes 
in the interior of degenerating Alge, proved to be such by 
vestiges of the chromatophore. They are filaments thickened 
at one end, and they execute wriggling movements. Hach 
vesicle or cell may contain only one or several of these bodies. 
They are only about ‘025 mm. in length, or a good deal 
smaller than the smaller sperms. They are doubtless similar 
in character to the “ parasitische Gebilde,” referred to by 
Béhmig (2)! and Sabussow (24, p. 377), and supposed by 
Monticelli to be spermatozoa. 
The female reproductive aperture leads into a thick-walled 
passage (figs. 2 and 17, ant.), which may be termed the 
antrum femininum. This is lined with columnar ciliated 
epithelium, outside of which is a thick muscular coat, com- 
posed of external circular and internal longitudinal layers. 
Perforating the wall and opening into the lumen of the 
antrum are the ducts of a great number of unicellular glands 
(gl.), which produce a secretion precisely similar in appear- 
ance to that of the granule-glands of the male apparatus. 
The ducts are dilated just before they open to form reservoirs 
for the secretion, so that a great quantity can be discharged 
very rapidly. When they are discharged the granules 
become disintegrated, and give rise to a nearly homogeneous 
mass with irregular granulations. 
From the antrum proper a passage runs upwards and 
forwards, and its upper extremity les immediately below the 
integument of the dorsal surface. During the breeding 
season, but not at other times, the dorsal wall of the body in 
1 I only know this paper through abstracts in the ‘ Zool. Jahresbericht ’ 
and ‘ Zool. Centralblatt.’ 
