THE TREMATODA 



59 



rectangular compartments (suckerlets). There is no anterior sucker 

 related to the mouth. The intestine is a simple sac like that of the 

 Rhabdocoele Turbellarians, and is entirely deprived of lateral caeca. 



FIG. VI. Aspidocotylea. 



1. Macraspis elegans, Olss., from the gall-bladder of Chimaera. (Altered from Monticelli.) 



2. Platyaspis lenoiri, Poir. (After Monticelli.) From the intestine of the Chelonian, 

 Tetrathyra vaillanti, from Africa. 



S.Catylogaster michaelis, Montic., from the fish Cantharus vulgaris. (Altered from 

 Monticelli.) 



4. Aspidogaster conchicola, v. Baer, from Anodon, etc. (After Monticelli.) g, the marginal 

 sense organs of the sucker. 



5, 6, 7. Three stages in the development of Aspidogaster. (After Voeltzkow.) In the 

 youngest freshly hatched embryo (5) the sucker is posterior and simple; the mouth is 

 provided with an oral sucker. In a later stage (6) the hinder end of the body has grown back- 

 wards, thrusting the posterior sucker on to the ventral surface ; the sucker itself has increased 

 in size, and a series of transverse muscular ridges has developed, dividing its cup into a 

 series of compartments ; the contractile sacs (j), which are at first apparent anterior to 

 the sucker, having during the process of growth been carried backwards beyond the hinder 

 margin of the sucker. In a later stage (7), of which only the posterior end is shown, the 

 process has gone still further ; a median ridge now divides each of the compartments into 

 two. By the appearance of a right and left lateral ridge the adult condition is brought about. 



8. Side view of an embryo at about the same stage as 5. 



The following letters have the same signification throughout : a, mouth ; b, genital pore ; 

 c, ventral sucker ; d, post-acetabular portion of the body in Aspidogaster; e, the curious tongue- 

 shaped prolongation of the sucker of the embryo, which ultimately disappears as the sucker 

 enlarges; /, pharynx; g, marginal sense organs in Aspidogaster; h, intestine; j, the pair of 

 contractile sacs, each with a concretion ; these sacs are the forerunners of the dilated portions 

 of the collecting tubes (b in Fig. VIII.) of the adult. 



Development is direct ; there is no ciliated larva ; there is no inter- 

 mediate host (see 35, 41, 44). 



FAMILY ASPIDOBOTHRIDAE, Burmeister. The single family has the 



