562 FEANK E. BEDDARD. 



layer of connective tissue and muscles belonging to the 

 pharyngeal wall. 



The development of these nephridia, so far as I have been 

 able to trace it (see on p. 574), seems to indicate that the 

 network in the body-wall is a secondary arrangement. It is 

 undoubtedly necessary to be very careful in arguing from on- 

 togeny to phylogeny, but so far as the facts go they seem to 

 point in this direction. In this case it will be hardly permis- 

 sible to compare the network to that of flat-worms^ particularly 

 of Cestodes ; in the Cestodes the nephridial network appears 

 to exist not only in the mesoderm, but also immediately 

 beneath the cuticle in the layers of the body-wall. 



On the other hand, it may be permissible to compare these 

 structures with something of the same kind in the Nematoids. 

 These worms usually possess at least remnants of a coelom 

 which is well developed, and with a limiting epithelium in 

 Gordius;^ in Ascaris, Joseph has stated (^ Zool. Anz.,' Bd. 

 V, p. 603) that it is possible to inject from the excretory pore 

 a fine system of canaliculi lying between the muscle-cells, and 

 in fact pervading the body generally, while Schneider (Mono- 

 graph Nematoden) has figured the branches in Ascaris. In 

 any case the canals running in the lateral lines are not a little 

 suggestive of the longitudinal canals which I have described in 

 Libyodrilus. In the Acanthocephala also, where there is a 

 coelom, the lemnisci, which have been stated to occur in certain 

 Nematoids also by Hamann, appear to be processes of the 

 body- walls depending into that coelom; they are permeated by 

 tubes which are connected with a system of vessels in the 

 body-walls. These tubes may be excretory in nature, though 

 they have been described as vascular. In any case I am not 

 aware that a similar network of tubes has been described in 

 the integument of any Oligochaeta ; this worm, therefore, has 



' According to Vejdovsky's recent work upon the structure of Gordius 

 (' Zeitschr. f. wiss. Zool./ Bd. xliii) these Nematoids show many points of 

 affinity with segmented worms ; so much so that they should be removed 

 altogether from Nemathalminthes. The excretory organs appear to be repre- 

 sented by coelomic canals. 



