462 



PARASITES OF ANIMALS 



furnished with spines. In other respects this genus nearly 

 corresponds with the distomes, the simple digestive tubes 

 bifurcating immediately below the cesophageal bulb. The speci- 

 men of Ech. hispidum here drawn (Fig. 77) was taken by me from 

 the spiral intestine of a sturgeon (1855), in which fish it occurs 

 very abundantly. The figure represents a back view of the 



head and a lateral view of the body, 

 the neck having been slightly twisted. 

 The ventral sucker is concealed, but 

 the transparency of the skin permits 

 a view of the internal organs. 



Another remarkable genus, estab- 

 lished by Von Siebold, is Gastero- 

 stoma. In this genus the ventral 

 sucker has taken the position usually 

 assigned to the oral opening; the 

 latter being near the centre of the 

 body. The digestive caeca also dis- 

 appear, leaving only a short sto- 

 machal cavity, which reminds one of 

 the same viscus in imperfectly or- 

 ganised sporocysts or rediae. When 

 O. gracilescens first came under my 

 observation I followed Rudolphi in 

 describing it as a distome (D. graci- 

 lescens). The anatomy of the genus 

 has been illustrated by Von Siebold ; 

 from whose observations also it may 

 be inferred that the larvae are various 

 forms of Bucephali. Prof. Molin de- 

 scribes the water- vascular or respi- 

 ratory apparatus as consisting (in G. 

 fimbriatum) of a broad central tube, 

 occupying the entire length of the 

 body and opening externally at the tail . 

 Amongst the more remarkable 

 fluke-types may be mentioned Van 

 Beneden's Nematobothrium (N. fla- 

 rina), occupying the branchial cavity 

 of Scitena aquila, also Holostoma 

 clavuSy found by Molin in the intes- 

 tines of Gadus merlucius, also KolliTferia filicollis, occupying 



1'iG. 78. Gastfrostoma graciltscens. 



Magnified. Original. 



