| OCR Text |
Show 1889.] NATURAL HISTORY OF DERO. 441 a complete list of literature referring to this genus, for the reason that Bousfield has gone into the matter somewhat fully. Concurrently with the development of the sexual organs, certain of the lower aquatic Oligochoeta have been stated to show other peculiarities, so that there is a kind of dimorphism among the individuals. The sexual individuals of Dero, in common with other Oligochaeta, show no traces of multiplication by budding ; connected with this is a regularity in the arrangement of the seta-bundles at the Fig. 1. Ventral aspect of sexually mature Dero. cp., spermathecal pores; 3 > male pores. distal extremity of the body. In the asexual form, on the contrary, the continual growth of the posterior groups of setae appears to produce an irregularity in the disposition of the seta-bundles ; the termination of these, for example, in D. perrieri (Bousfield) (see PROC. ZOOL. Soc-1889, No. XXX. 30 |
