269 



cells of the large accessory gland (which probably secretes 

 the cementing material of the spermatophors — Pachydcrtnon 

 of Claparede)/ situate on the efferent canal of the male 

 organs in Tubifex and Limnodrilus also, at the end of the 

 season of sexual reproduction, become broken up and dis- 

 charged into the perivisceral cavity, where they float. 



These facts of the separation of cells from various organs to 

 float in the fluid of a large cavity, would not be worthy of 

 particular attention if we regarded them as simply thrown off 

 to be got rid of, and as having no further function when once 

 floating in the perivisceral fluid. Such a view cannot, how- 

 ever, be held, for the perivisceral fluid, as before observed, is 

 a highly-organized liquid, like the blood ; and the cells, after 

 becoming detached, and in fact migrating into it, are not 

 found to be dead, but remain there for some time, slightly 

 changing their form, and performing some part or function 

 which has importance in the worm's economy. What that 

 may be it is not easy to determine, but I think there can be 

 no doubt that there is gradual absorption of such corpuscles 

 as those from the generative organs — perhaps of all. Very 

 characteristic large corpuscles, with excessively fine radiating 

 processes which originate in the exuberant male generative 

 glands after reproduction in Tubifex, are still to be found 

 in the perivisceral fluid in October, in some numbers, 

 though slightly shrunken in size, so that the absorption 

 in that case does not appear to be very rapid, (PI. XVII, 

 fig. 2.) If one of the functions of the perivisceral fluid 

 be the reassimilation of living matter which has attained 

 a condition unfitted for the Avork of the part in which it 

 originally developed, and this be the explanation of the 

 migration of hepatic, muscular, endothelial, and generative 

 gland-cells into a common reservoir, can we find any parallel 

 to such a process in the breaking up of blood-corpuscles in 

 the spleen or elsewhere ? If, on the other hand, the migrated 

 cellular elements of the perivisceral fluid have more active 

 functions, and are not destined to be simply absorbed, may 

 Ave not see in their change of function and position a parallel 

 to some of the cases already noted in Vertebrata, and men- 

 tioned at the beginning of these remarks ? 



Remarkable stellate pigment cells forming bands of colour, 

 and belonging to the Endothelium, are sketched in PL 

 XVII, fig. 7. They are from an unidentified species of 

 Limnodrilus occurring in the Thames, near Barking. 



^ See April number, page 148. I have this spring studied the spermato- 

 phors carefullyj and have ascertained their mode of lormatiou, &c. 



