30 Mr. H. J. Carter on the Spermatologij of a new species of Nais. 



Testes. 



The so-called testes (fig. 2 b and 3 d) are situated immediately 

 in front of the reproductive band, and consist of simple con- 

 tractile sacs opening externally by a short duct (d) close to the 

 anterior border of this band. They may be empty, or contain 

 spermatozoa in bundles {a, a), the cause of which bundling will 

 ajipcar hereafter. Witli the spermatozoa are generally a number 

 of loose, irregular, hard granules (6«), and an albimiinous mass, 

 which will be seen, by-and-by, to be the effete remains of the 

 spermatophorous elements. I have also observed cells (c) pre- 

 sent in the anterior part of the sac, like those of the reproduc- 

 tive band and peritoneal cavity, but with some brown matter in 

 each, which is particularly deserving of attention, because it will 

 be found hereafter to mark the sperm-cell throughout. Lastly, 

 in one instance, four small globular masses of granules [d), from 

 which radiated, in all directions, attenuated linear bodies re- 

 sembling the spermatozoa at an early stage of growth, were 

 forced out from the testicular sacs; but beyond this, the so- 

 called testes in Nais fusca have not afforded me any other stage 

 in the growth of the spermatozoa, with the exception of the full 

 development, although many scores have come under my ob- 

 servation. The fully-developed spermatozoon (fig. 6 b) is about 

 l-160th of an inch in length, linear, and so narrow that I have 

 never been able to see its attenuated extremities satisfactorily 

 with a magnifying power of 450 diameters. 



It may now be asked, from whence the cells come, from which 

 the spermatozoa are developed, — assuming that which will be 

 proved hereafter, viz. that those cells which were observed in 

 the testes with the brown matter in them were undoubtedly 

 spermatic cells ? In reply to which I can only state, that, much 

 as I have sought for a duct in the so-called testis communicating 

 with the peritoneal cavity (and much as, uj)riori, wc might expect 

 one to exist like that of the segmental organ (fig. 3 o) and the 

 so-called fallopian tubes (fig. 3 e') leading into the ovisacs, from 

 the testicular sac and oviduct being but mere modifications of 

 the segmental organ), I have not been able to find any; while 

 the contour of the testes being so neatly defined, and the con- 

 tents, on pressure, always escaping through the external orifice, 

 leads me to the conclusion that there is none. Again, the testes 

 being filled with spermatozoa only when the reproductive band 

 is well developed, and empty and contracted when it is absent, 

 leads one further to infer that the rc])roductive band is in some 

 way connected with the testes ; and that the cells of which it is 



in Planaria, &c. The moveincut of the cilium in Spirostoma was j)rc- 

 eisely that of the line in fly-fishing. 



