22 



G. O. SAES. 



[Xo. 8. 



like body of a rather firm, but elastic consistency. On inspection by 

 the aid of a high magnifying power, the thread has the appear- 

 ance of being built up by 2 threads twined together and exhibiting 

 „en miniature" a quite similar aspect as a common cable (see figs 

 12, 13), the twining being now at the right, now at the left; some- 

 times even the appearance of a double plaiting may be conveyed 

 to us, and in fact Zencker has given a figure indicating such an 

 arrangement. By the application of the strongest and most im- 

 proved immersion-lenses, in connection with a sufficiently com- 

 plete illuminating apparatus, we may, however, find that this 

 apparent plaited structure of the spermatozoon merely depends 

 on an optical illusion. It will, on the other hand, not be very 

 difficult to detect a central axis running through the whole 

 spermatozoon, and upon this axis but a single band-like body 

 is twined in more or less close circumvolutions. At the one 

 extremity (see fig. 12) these circumvolutions become rapidly looser 

 and more distant, and at the same time the spermatozoon con- 

 siderably diminishes in thickness, forming at last a very narrow 

 rod, along which a thin lamella is seen to wind in loose spiral 

 turns; the edges of this plate, alternately projecting on either 

 side, may under less powerful magnifying powers easily convey 

 upon us the impression of as many fine recurved spines, and 

 have also been represented in this manner by some naturalists. 

 The cable-like appearance of the . chief part of the spermatozoon 

 is thus evidently effected by the circumvolutions of the above 

 mentioned spiral plate lying in close contact with each other 

 (see fig. 14). The opposite extremity of the spermatozoon, which 

 may be named the upper or anterior, since the spermatozoon 

 would seem constantly to be expelled with this extremity for- 

 wards, terminates (fig. 13) quite abruptly in a pelucid, somewhat 

 flexuous point, sharply marked off from the body of the sper- 

 matozoon, which until its base exhibits the densely coiled appear- 

 ance described above. 



Biological Observations. - Two specimens of this species, 

 both adult females, were observed as early as 1884 in one of 

 my aquaries, prepared with mud sent by Mr. Lumholtz from the 



