141 



booklets, which he compared to the crown of booklets of 

 the Cestoid worms. 



In his memoir on tlie development of the Entozoa, G. 

 Wagener figures the embryo of Distoma tereticolle carrying 

 in front a complete crown, composed of two score of strise, 

 which are, he says, like booklets.^ 



I have myself studied the embryo of this Trcmatod Avhich 

 bad been incompletely studied by G. Wagener, and which 

 be has figured without bringing out clearly the dis- 

 tinctive characters which it presents. 



The embryo carries round the anterior enlargement of the 

 body four little plates, of a triangular form, similar one to 

 another, and disposed symmetrically. Each of them formed 

 by a thickening of the cuticle carries a system of booklets. 

 These booklets are very small, and present, at a short 

 distance from their point, a little swelling, which gives them 

 a peculiar aspect. 



These plates are supported by the anterior extremity of the 

 body, which is greatly enlarged; where they are disposed at 

 the extremity of two diameters, cutting each other at right 

 angles. There is here, then, a quadrilateral symmetry. 



Near the posterior extremity of the body exists a circular 

 zone of little ray-like fine bristles, which completely surround 

 the body of the embryo. 



I could not distinguish in the cellular mass of the body 

 any trace of digestive tube nor any appearance of excretory 

 canals. 



It is imjDOssible to overlook the analogy which the embryo 

 of Nematobothrium presents to those of Distoma tereticolle 

 and D. variegatum and of Monostoma filum ; and it seems to 

 me evident that the animal which forms the subject of this 

 note ought to be ranged by the side of those Trematods in 

 the group of Trematoda digenetica, with non-ciliated 

 embryos. Their embryonic form is characterised — 1st, by 

 the absence of vibratile cilia ; 2nd, by the swelling of the 

 anterior part of the body, separated from the posterior part 

 by a circular furrow ; 3rd, by the presence around the 

 cephalic extremity of a series of booklets or prickles, the 

 form and disposition of which varies slightly in the three 

 genera. 



The embryonic characters come then to the support of 

 the conclusion which M. P. J. Van Beneden had drawn 

 from the study of the organisation of Nematobothrium, and 



* G. Wagener " Beitrage znr Entwickelungs^eschichte der Eiiigeweide- 

 wiirmer," page 25, pi. xx, in ' Natuurkundige Verhandelingeu van de Holl. 

 maatscli, der Weteuschappen te Haarlem,' 2Qd Verz., 13th sect. 



