2 18 SUMMARY OF CURRENT RESEARCHES RELATING TO 



highly developed worms, and their development is to be regarded as 

 intimately associated with that of the segmentally arranged coelomic 

 cliambers, such as are at any rate but feebly represented in the 

 Hirudinea. 



(4) In connection with these numerous nephridial tubes many 

 external openings leading into the still persisting network are formed 

 (e. g. Perichseta aspergillum). 



(5) The small nephridia become aggregated into groups, the aggrega- 

 tion commencing in the posterior region of the body (as in Acanihoporus 

 multiporus and MegascoUdes aiistralis). As the aggregation proceeds the 

 external openings diminish in number, and the network lessens in 

 extent. 



(6) The formation of large nephridia, either out of an aggregate of 

 small nephridia, or by the special growth of one of an aggregation of 

 small nephridia. Each large nephridium acquires secondarily an 

 internal opening into the coelom. These openings, which have a very 

 definite relationship to the coelomic chambers, must be supposed to be 

 new formations within the group. 



(7) The final disappearance of all trace of the small nephridia, and 

 with them of the network and longitudinal duct. Then there remains 

 in each segment, as in most adult earthworms, a limited number — usually 

 one pair — of large nephridia, with internal and external openings. 



When it is considered that the character of a nephridium is that in 

 some part of the funnel-shaped structure the duct is not intercellular, but 

 the funnel bends back into an intracellular duct, always of considerable 

 length and complication, and never absent, while the whole of the genital 

 duct is intercellular, we see that there is little reason for supposing that 

 the latter is a modified nephridium. The testes can, apparently, be 

 found at any time of the year, and closely resemble the ovaries — of 

 which there is one pair — externally. Spermatozoa undergo their develop- 

 ment in the vesiculse seminales, which are broken up into a great series 

 of capsular chambers. 



Structure of Urochaeta and Dichogaster, and Nephridia of Earth- 

 worms.* — Mr. F, E. Beddard has some notes on the structure of Uro- 

 chseta in supplement to and criticism of Prof. Perrier's memoir on this 

 earthworm. Mr. Beddard cannot believe that there are in it any pores 

 which put the haemal system into communication with the surrounding 

 medium. The mucous glands described by Perrier may be shown to be 

 nephridial in character by the presence of coelomic funnels which agree 

 in their structure with the funnels of the nephridia in the other seg- 

 ments of the body ; from the typical nephridium the gland differs by its 

 branched character and the presence of several coelomic funnels ; the 

 author concludes that the mucous gland is a branched nephridium, of 

 which the greater number of branches end blindly, while a few open 

 into the coelom by ciliated funnels. In Dichogaster g. n. (D. Damonis 

 sp. n. from Fiji) the mucous gland has no coelomic funnel, and the duct 

 opens, not on the exterior of the body, as in Urochseta, but into the 

 buccal cavity, and, lastly, it appears to be formed by a simple much 

 coiled tube. Mr. Beddard thinks there is evidence that the specializa- 

 tion of this part of the nephridial system ultimately led to the concen- 

 tration of the numerous excretory pores into one long duct ; in other 



* Quart. Journ. Micr. Sci., xxix. (1888; pp. 235-82 (2 pis.;. 



