ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 221 



projects into the segment in front ; this soon gets a lumen in which 

 a very long active cilium may be seen; this closed ciliated cell appears 

 to be wanting to the pronepbridia of the Lumbricidae ; the orifice of 

 the cell may be called the pronephrostom. Just behind the dissepiment 

 the cells of the cord increase and gradually form a lobe which grows 

 dorsally and forms loops ; this lobe corresponds to the dorsal cell group 

 in the solid cords of Lumbricida3. The ciliated cell of the pronephro- 

 stom has meanwhile divided several times until at last it becomes con- 

 verted into a plate-like structure, at the margin of which fine and short 

 cilia begin to beat. In this way the pronephrostom is converted into 

 the funnel of the definite excretory organ, and it becomes continuous 

 with the duct which, later on 5 appears in the dorsal lobe. Finally, the 

 remainder of the primitively straight cord acquires a lumen, and as soon 

 as the contractile bladder is formed by the invagination of the hypoder- 

 mis the definite nephridium is in full activity. 



It follows from this description that we have in the Annulata to 

 distinguish three kinds of excretory organs : — 



(1) Larval excretory organs which have nothing in common with the 

 definite organs. 



(2) Pronepbridia of developing segments which only function for a 

 short time. 



(3) Nephridia, developed from the pronepbridia ; these degenerate 

 in the second to sixth segments of most Oligochaetes, but are found in 

 those that succeed them. 



Reproductive Organs of Moniligaster.* — Mr. F. E. Beddard thinks 

 that the account given by M. Terrier of the reproductive organs of Moni- 

 ligaster deshayesi is incorrect, but that his description may bo brought 

 more into accord with those of Dr. Horst and himself. Ho points out 

 that in numerous characters the reproductive organs of this worm re- 

 semble certain limicolous forms ; such are the identity of the " prostate " 

 with the atrium of Stylaria lacustris ; the funnel of the vas deferens is 

 a simple disc-shaped expansion, and not plicated ; the vasa deferentia 

 themselves resemble those of the Naidomorpha in being single, and in 

 being contained in two segments ; and the male pores are placed on the 

 boundary line between two segments, as is commonly the case among 

 limicolous, but never the case in terricolous Oligochaites. These facts 

 may be urged against the division of Oligochseta suggested by Claparede 

 and endorsed by many systematic writers. 



So-called Prostate Glands of Oligochseta.t — Mr. F. E. Beddard 

 points out that the vasa deferentia of some earthworjus are not furnished 

 with any special glands (e.g. Lumbricus, Microchseta). Where such are 

 present they belong to one or other of two types; in Acaniliodrilus, 

 Trigaster, and others, tbey have the form of an elongated, often contorted, 

 tube, of an opaque white colour ; in Perichseta, Megascolex, and others, 

 they are composed of numerous lobules, more or less loosely connected 

 together, and opening by a number of ductules into a common duct. 

 When we investigate the two questions — Do these various structures 

 correspond to each other? and, Are they homologous with any organs 

 found among the lower Oligochasta ? — we are led to the conclusion that 

 the so-called prostate of Perichseta is the homologue of the atrium in 

 other earthworms and in the Limicohe ; it is, then, clear that under the 



* Zool. Anzeig., x. (18S7) pp. G78 81. t Ibid., pp. 675-8. 



1888. R 



