139 



lets. The little prickles, which alternate with those which 

 I have just described, are placed in the peripheral part of 

 the disc. They are straight, very slender, and do not 

 present, I believe, any median enlargement. In the sectors 

 M and N (figs. 4 and 8), very minute booklets are implanted 

 of great delicacy, which are all disposed in a radiate fashion 

 on the disc, and are situated at equal distance from one 

 another, without our being able to discover any regular order 

 in their disposition. 



All these booklets, those of the sectors A and B, as well 

 as those of the sectors M and N, are implanted in the sub- 

 stance of the disc for the greater part of their length ; their 

 points alone are free, and project a little from the edge of 

 the disc when seen in projection. 



If the surface of the disc is examined with care, concentric 

 transverse striations can be observed, Avhich speak to the 

 existence of muscular fibres (?) , the presence of which appears 

 to be indisj)ensable, in order that the embryo may avail itself 

 of the crown of booklets. 



At the centre of the disc is seen a small circular space, 

 much darker, appearing like a black spot. It is exceedingly 

 difficult to determine the nature of this organ, on account of 

 the extreme minuteness of the embryo. It, however, appears 

 to me scarcely doubtful that the central spot of the disc of 

 Nematobothrium has the same signification as the organ 

 which G. Wagener has considered as a true orifice in the 

 embryos of several Trematoids and of various Echino- 

 rhynchi.^ Is it a sucker ? is it really an orifice ? This point 

 I have not been able to settle in the animal which now 

 occupies our attention. 



The disc is the part of the body of the embryo which 

 presents the greatest consistence. The body possesses great 

 mobility, and its length augments and diminishes in inverse 

 proportion to its breadth, during the movements which the 

 embryo executes. 



Structure. — The body of the young Nematobothrium is 

 covered by a cuticular membrane of some thickness. Under 

 this cuticle a cellular mass is found, composed of clear and 

 transparent cells of extreme delicacy, and of very small 

 dimensions. There are also distinguishable small refrangent 

 globules, of which some are fatty in nature, others mineral, 

 probably calcareous. 



G. Wagener^ and other helminthologists have recognised 



* G. Wageuer, " Helminthologis cbe Bemerkungen aus einem Send- 

 schreiben an C. Th. v. Siebold," ' Zeitscbrift fiir Wiss. Zool.,' Bd. h., pi. v 

 and vi. 



^ G. Wagener, loc. cit. 



