ON TUBIFEX RIVULORUM. 169 



for the conclusion that the supposed parasitic infusorium of 

 Claparede is not an animalcule at all, but an aggregation of sper- 

 matozoa embedded in a cementing matrix, and constituting a sperm- 

 rope or spermatophore (Fig. 4), moulded in a spiral manner in the 

 long neck of the seminal receptacle, and having a conical head, 

 corresponding to an invagination in the wall of this neck at its 

 commencement. They may sometimes, he says, be seen lying in 

 this position in course of being moulded, and in confirmation of 

 this he observes that in Ttibifex nmbelUfer, an allied species, where 

 the reduplication of the neck of the pouch is wanting, the sper- 

 matophores are also destitute of the conical head. The spermatozoa 

 and the cementing matrix, he says, must be introduced in a viscid 

 form, through the intromittent organ of one worm into the recep- 

 tacle of another. 



The elucidation of the various questions suggested by the 

 foregoing would furnish ample material for a long and careful 

 investigation on the part of any of our members who might be 

 sufficiently interested in the subject ; the observation, for instance, 

 of the act of oviposition, which, involving as it does the question 

 of the oviduct, would probably require much patient and contin- 

 uous study, but would also clear up a great deal that is obscure in 

 the history and organisation of these annelids. I must, however, 

 content myself with the humbler task of taking the organs 

 enumerated by Claparede seriatim, and making such remarks 

 thereupon as my own imperfect observations may suggest as 

 worthy the attention, especially of those of our members whose 

 acquaintance with the subject may be entirely new. 



The presence of the glandular cincture which surrounds the 

 reproductive segments, presents an obstacle to the observation of 

 the organs, not found in the other parts. It is only, therefore, by 

 slight pressure in a compressorium, or otherwise, that they can be 

 made out in the living state. Viewed in this manner, the testes in 

 mature specimens may be seen to be filled with spermatozoa and 

 sperm-cells in all stages of development, and with the application 

 of a little more pressure, these may be made to escape, by the 

 rupture of the body, into the surrounding water, where they will 

 be more readily observed. The sperm-cells present the varied 

 appearances figured in Plate 34, Fig. 5 ; all of which represent 

 different stages in the development of the spermatozoa, from the 



