588 SUMMAEY OF CUERENT RESEARCHES RELATING TO 



due to the presence of two egg-sacs as large as the body. The form and 

 appendages are described. 



(6) The male, which is much rarer and decidedly smaller, resembles 

 a Cyclops. It differs markedly in the structure of the first and second 

 thoracic appendages. 



(c) Reproduction goes on from May to September ; two or three egg- 

 laden females may occur on one AmpMura ; the segmentation is total and 

 unequal ; the gastrulafcion epibolic ; the embryo a nauplius. The young 

 forms fix themselves to the extremities of the arms of the Ampliiura, and 

 approach the disc as they grow. 



In most of its characters, Cancerilla tuhulata approaches Ascomyzon 

 echinicola Norman, a parasite of Echinus esculenius, and Asterocheres 

 lillyehorgii Axel Boeck, a parasite of Echinaster sanguinolentus. Its buccal 

 armature connects the Poecilostomata with the Siphonostomata, and 

 M. Giard proposes to unite the Lichomolgidae Kossmann (Sapphirinidae 

 Brady), the Ascomyzon tid^e Axel Boeck (Artotrogidte Brady), the Bomolo- 

 chid?e Claus, and the Ergasilidse Claus, in a single group of Coryceidse. 



Vermes. 

 a. Annelida. 



Origin of Excretory System of Earthworms.*— Prof. E. B. Wilson, 

 who has studied the development of Lumhricus oUdus, finds a remarkable 

 similarity between the development of its nephridia and the origin of the 

 excretory system in Vertebrates. Of the eight large cells at the hinder end 

 of the embryo two are nephroblasts ; from each cell a row of cells extends 

 forwards on the ventral side of the body ; the rows are at first one cell 

 wide, but become solid cords, several cells in thickness ; in each somite a 

 solid outgrowth from each nephridial row projects into the coelom, and is 

 ultimately converted into a nephridium ; as these organs arise as metameric 

 outgrowths from a solid cord of cells that lies in the somatopleure, their 

 mode of development is essentially similar to that of the vertebrate prone- 

 phros. The nephroblast is originally an ectoblastic cell, and later sinks 

 below the surface. Hatschek, Meyer, and Lang have called attention to 

 the close resemblance between the Wolffian ducts of vertebrates and the 

 longitudinal canal that unites the nephridia of the larval Polygordius and 

 some adult annelids ; the present results supply the embryological proof of 

 the homology of the two structures, and show that the excretory system of 

 annelids and vertebrates are constructed on fundamentally the same type, 

 and originate by similar modes of development. 



Polychseta of Linard.f — M. le Baron de Saint-Joseph deals in this 

 first portion of his memoir with the SyllidaB ; in his introduction he speaks 

 of the importance of examining Annelids in the living condition, pointing 

 out that large species can only be preserved in alcohol, which destroys 

 their colours and contracts their tissues, while all the media in which 

 smaller forms are mounted have their inconveniences. The best — or, 

 rather, the least objectionable — is Langerhans's fluid, which consists of five 

 parts of gum arabic and five of distilled water, to which, after twenty-four 

 hours, are added five parts of glycerin and ten of a five per cent, solution 

 of phenic acid; before being put in this the worm should be plunged in a 

 one per cent, solution of chromic acid, which kills it without causing so 

 much contraction as alcohol. 



* Proc. Acad. Nat. Sci. Philad., 1887, pp. 49-50. 

 t Ann. Sci. Nat., i. (1887) pp. 127-270 (6 pis.). 



