224 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of labour between tho anterior and posterior nephridia. In tbo former 

 the epithelium of the extraordinarily well-developed tubular portion has 

 a very large excretory surface, and the pigmented lymph-glands are in 

 their neighbourhood. In the seasons when the sexual organs are in- 

 active it is probable that the chief function of the hinder nephridia is to 

 destroy and remove the used up lymjdi-corpuseles from the body. When 

 the gonads are active they take up their products from the ccelom and 

 conduct them to the exterior. 



The development of the permanent nephridia of Pohjmnia nebulosa 

 is next described ; and this is succeeded by an account of the larval 

 organs. 



Passiug to morphological conclusions, the author discusses the rela- 

 tions between the ciliated funnel, the nephridial tube, and efferent canal, 

 and the morphological relation of the nephridial passages to the tubes. 

 The funnels are shown by the history of development in Pohjmnia to bo 

 peritoneal funnels in the true sense of the word ; the nephridial tubes 

 arise from a retro-peritoneal tissue, and are therefore morphologically 

 distinct from the peritoneal funnels. With regard to the efferent canals, 

 the continuity of their epithelium with the hypodermis, the histological 

 resemblances between them and certain parts of the skin, and their sharp 

 limitation from the inner cell-layer of the nephridial tube speak to their 

 ectodermic origin. The passages appear to have arisen from one and 

 the same embryonic tissue as the nephridial ducts. The typical condi- 

 tion of the funnels, and the influence exerted on them by the change of 

 the branchiae and branchial vessels are next considered ; and this is fol- 

 lowed by a consideration of the significance of the renal septa in Amplii- 

 trite rubra. The ancestors of the existing Terebelloidea must have had 

 nephridia in the whole of the thorax, and the ciliated infundibula of 

 these were all provided with the upper lips which are typical for this 

 group. 



The author believes that the information he has acquired justifies a 

 reconstruction of the nephridial system of the nearest ancestors of Lanice 

 and Loimia ; they had, he thinks, two long nephridial ducts, which began 

 anteriorly in the third somite and extended uninterruptedly through, 

 at least, the whole thorax ; in each segment there was a pair of nephri- 

 dial tubes with typical infundibula, and there were as many efferent 

 ducts in the external pores. He does not now attempt to homologize 

 this arrangement with that of the archinephric system of Vertebrates, 

 and contents himself with comparing the two from a purely anatomical 

 standpoint. It will be remembered that Mr. J. T. Cunningham pub- 

 lished a short time ago * an account of his observations on the nephridia 

 of Lanice conchilega. Herr Meyer points out the few points in which 

 his observations diverge from those of the English anatomist. 



With the remaining portions of Herr Meyer's paper we must deal 

 much more briefly. The excretory and genital organs of the Cirratulidaa 

 are next considered, a detailed account being given of the nephridia of 

 Chsetozone setosa ; the vascular system and the peritoneal glands are also 

 described. The concluding section deals with the nephridial system of 

 the Serpulaceae and Hermellidse ; the hinder organs or genital tubes 

 of these groups agree generally with the typical annelidan nephridium, 

 but the thoracic nephridia offer some very remarkable differences. The 



* See this Journal, 1837, p. 591. 



