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Mr. A. G. Bourne. 



[June 21, 



The organs which, in animals possessing a well-developed ccelom, 

 lie within that ccelom, either get blocked ont by connective tissne 

 growth or remain enclosed in the remnants. The same organs may 

 remain in different remnants in different genera. No better instance 

 can be given of this than the varying position of the nephridial fnnnel 

 in Glepsine, Pontobdella, and Hiruclo. 



The lnmen of the existing ccelom, as above described, comes into 

 commnnication with the lnmen of a true vascular system, which was 

 probably either derived at a very early period from the archaic 

 enterocoele, or was formed independently by hollowing in connective 

 tissue cells. That the communication between the two is of a 

 secondary nature, and not a persistence of the original communica- 

 tion, which must have existed if one developed from the other, is 

 indicated by the existence of colourless amoeboid cells in the ovarian 

 sac and around the vas deferens in Hiruclo. These were probably 

 closed at a very early period before the development of haemoglobin. 

 This may have a phylogenetic bearing only, but it may very possibly 

 be a process which is repeated ontogenetically. 



The development of new ccelomic space (botryoidal tissue) may be 

 termed pseudocoelosis. 



That this new space is " ccelomic " is amply demonstrated by the 

 fact that in its highest development it encloses the nephridial funnel 

 (Nephelis), and, further, that such perinephrostomatous portions of it 

 may acquire a definite musculature and the " botryoidal " cells become 

 modified to form a secondary ccelomic epithelium. The interpretation 

 which the author would put upon this process is that an archaic 

 enterocoele gradually undergoes diacoelosis, being replaced by a pseudo- 

 coele. This primary and secondary ccelom exist simultaneously side 

 by side in all existing Gnathobdellidee. 



In the Rhyncobdellida3 considerably more of the primary ccelom 

 remains, and the secondary coelorn has not yet appeared upon the 

 scene. 



Nephridia. 



The nephridia are in all cases tubular organs, opening on the one 

 hand into the ccelom. and on the other to the exterior. 



The funnel, the opening to the ccelom, exists in all the genera, 

 although its existence in Hiruclo and allied genera has always been 

 denied, but it has long been known to exist in Glepsine, Nephelis, and 

 had also been described in Pontobdella. 



The condition of these funnels presents a serial modification. In 

 Glepsine and Pontobdella they are fairly simple, but in Nephelis and 

 Trocheta they become drawn out into lobes, and in Hirudo and its 

 allies this process has been carried to an extreme, the central lumen 



