100 ENTOZOA. 



from tlie testes in a downward direction, becoming suddenly and 

 enormously dilated to form two large seminal reservoirs, which 

 latter finally communicate below with the sac or sheath of the 

 penis. In the female the reproductive elements are very peculiar ; 

 for, in place of a pair of distinct ovaries, we find the general cavity 

 of the body to contain a number of free, well-defined, rounded 

 masses, which develope the eggs within their substance. Two of 

 these egg-bearing masses are shown in the annexed plate (figs. 3 

 and 5) ; the former representing an early stage where the organ 

 consists, for the most part, of spherical nucleated vesicles, the 

 latter giving a more advanced stage where some of the vesicles 

 have become much elongated. In fig. 4 the isolated vesicles are 

 seen to display nucleoli as well as nuclei. By ftirther development 

 after their escape from the so-called free ovaries, or egg-bearing 

 masses, these vesicular bodies come to represent, as it were, the 

 several egg-envelopes, so that in a much more advanced egg we 

 have, at length (as in figs. 6, 7, and 8), an outer envelope, a middle 

 covering (which is coloured in at least one species of Bchinorhyn- 

 chus, and probably forms the true shell or chorion), and an internal 

 or third layer. The middle layer is usually constricted at either 

 pole, somewhat after the fashion observed in the egg-shells of 

 Trichocephalus. The third membrane is well shown in the two 

 highly-magmfied ova drawn by Mr. Busk (Fig. 13). These are 

 referable to EchinorhyncJms angustatus. In the advanced eggs of 

 E. anthuris I have particularly noticed the lateral disposition of 

 a finely granular mass (figs. 7 and 8), which appears to he between 

 the true egg-shell and the external envelope. This- mass is, there- 

 fore, not the yolk itself, but a formative granular mass, similar to 

 that which we find in the nascent ovum of Tcenia solium. It is, in 

 pomt of fact, the matrix, part of which is speciahsed or set aside to 

 form the yolk, whilst the remainder shows itself as a superfluous 

 heap of granules lodged between the outer primitive envelope 

 and the chorion. Possibly the. latter may subserve a nutrient 

 pui'pose. 



