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evident incipient ovaries in the usual place. Notwithstanding their small size, they exhibited 

 already distinctly their characteristic form and ramification (see fig. 9, 10). The fully deve- 

 loped ovaries are of a more or less intense reddish yellow color, and are already hereby 

 immediately distinguishable from the spermaries, which are always of a lighter whitish 

 color. The skin which surrounds the various ovarian tubes is rather firm, fibrous and semi- 

 transparent; so that the ova-cells inside may be seen through them more or less distinctly 

 (see fig. 4, 11). 



On examining the contents of such a tube, there will be found egg-cells very diffe- 

 rently developed. The smallest of them (fig. 12, 13), which can only with difficulty be di- 

 stinguished irom the epithelial cells that line the inside of the wall of the tube, are per- 

 fectly pellucid, often of an irregular form, and without any distinct exterior membrane, but 

 all furnished with a large and well defined nucleus (germinative vesicle) wherein there may 

 usually be distinguished a single small nucleolus (germinative point). The larger egg-cells 

 (fig. 1-1, 15) appear more isolated in the interior of the tube, and are sometimes quite 

 detached from the walls. In them there may already be discerned a distinct light enveloping 

 membrane (corion) and a greater or smaller quantity of reddish yellow yolk deposited in the 

 cell-plasma, which makes them less transparent. Finally in the largest egg-cells (fig. 16) 

 which always lie completely free in the interior of the ovarian tubes, this mass of yolk has 

 increased so much, that the whole egg-cell, with exception of the clear enveloping membrane, 

 becomes quite untransparent, and the germinative vesicle is usually quite hidden. In this state 

 the egg seems to have arrived at maturity, and is then carried out by the ovarian ducts. 



b. The spermaries (testes). 



The spermaries (fig. 17, 18, 19) correspond, in their general form and arrangement on 

 the whole, to the ovaries; but are easily distinguished from the latter by their lighter whitish 

 color, and by the single tubes or caeca not being simply cylindrical, but in many ways bent 

 and lobed, whereby the whole organ exhibits a still more complicated appearance than the 

 ovaries. In young specimens (see fig^ 18, 20) the single caeca may usually be traced in 

 their whole length, as narrow tubes nearly of uniform thickness, but bent in and out at 

 short intervals or zig-zagged, and gradually uniting themselves to a certain number of con- 

 verging main-trunks. These are at last connected in a single short exit, which issues at 

 the same place as the ovaries in the females (fig. 19 a). In older specimen? the single caeca 

 often form (see fig. 17) as is the case with the ovaries, large sack-like enlargements, which 

 externally exhibit innumerable small rounded lobes. If one of the extremities of the caeca 

 is viewed under a microscope, it will be found (see fig. 21) that their interior is, as it were, 

 divided into a number of irregular spaces, wherein are found numerous small clear elliptic 

 bodies with a great number of interior nuclei. These bodies (fig. 22) represent the deve- 

 loping cells of the spermatozoa. In the larger sack-like extensions we find the fully deve- 



