170 ON TUBIFEX RIVULORUM. 



primitive testis cells. These changes have been described by 

 Bloomfield * as follows : — The primitive testis cell subdivides and 

 becomes a sperm polyplast, which consists of a number of small 

 cells, spermatoblasts, surrounding a larger one, the blastophore. 

 The spermatoblasts multiply by fission whilst remaining side by 

 side, and ultimately assume an elongated form, being that of the 

 ripe spermatozoa. The function of the blastophore appears to be 

 merely that of a carrier of the spermatozoa during their develop- 

 ment, and it ultimately shrivels and perishes. Changes some- 

 what similar have been observed to take place through a wide 

 range of animal forms. 



The ripe spermatozoa, set free from the blastophores, escape, 

 as Claparede says, by rupture of the testicular wall, into the 

 perivisceral cavity of the tenth and eleventh segments, where they 

 are taken up by the cilia fringing the funnel-shaped internal orifices 

 of the vasa deferentia. These funnels are not very easy to make 

 out ; they may, however, be discerned just below the seminal 

 receptacles. The ciliary tube has in addition to its coating of 

 fusiform fibres described by Claparede, an external epithelium, as 

 shown in Fig. 6. Although I have seen this very clearly, on one or 

 two occasions, it is not always separable from the internal layer. 

 The ciHa which line the interior of the tube sometimes produce, 

 by their action, a very pretty running pattern, as shown in Fig. 7. 

 The structure and appearance of the atrium, with its seminal 

 vesicle, as also of the intromittent organ, I will leave mainly to be 

 gathered from Claparede's figure. I will observe of the atrium 

 that its glandular lining, which Claparede has figured as consisting 

 of rounded cells, would appear to me to be more correctly 

 represented by my Fig. 8. On one occasion I found, attached to 

 its external wall, a number of very delicate, transparent, leaf-like 

 objects, as in Fig. 9, amongst which were others, shorter, and of a 

 clavate form ; but I have not the least idea what they were. The 

 seminal vesicle (Lankester's cement gland), I have found to be 

 occupied with a mass of small nucleated cells, each containing a 

 few granules, and al)Out one-thousandth of an inch in diameter; 

 a and b, Fig. 10, represent the ovaries. In the former the external 

 cells only are seen, these are in their earliest stage ; others more 

 advanced are seen in Fig. 10, b, to occupy the centre of the organ, 

 and these show the germinal vesicle and spot very distinctly. 

 * Quar. Journ. Mic. Sci., vol. 20, 1880. 



