The life history of Diplodiscus temporatus Stafford. 603 



the redia of Diplodiscus temporatus, seem according to Looss' (1892) 

 figures to be entirely wanting in the redia of Amphistomum (Diplo- 

 discus) suhclavatiim. His figures (9 and 10 tab. 20) show the redia 

 of that species to be comparatively narrow at the anterior end, from 

 which it increases rapidly in diameter for about one fifth of its 

 length. From this point it tapers quite regularly toward the posterior 

 end which (fig. 10 tab. 20) is sharply pointed. The intestine is 

 very short, and flask-shaped, in all of the developmental stages of 

 the rediae figured. In D. temporatus the gut is comparatively long, 

 frequently extending nearly the entire length of the body cavitj-. 

 It usually lies close against the body wall along the ventral side 

 of the redia. 



EossBACH (1906) has called attention to the fact that the early 

 stages in the development of the redia of Amphistomum suhclavatum, 

 as figured by Looss, difter very much from the conditions found in 

 most of the other species of Distomae. The j'oungest redia figured 

 by Looss, which is as yet (fig. 1 tab. 20) only a small sac-like 

 structure scarcely one fourth the length of the fully developed redia, 

 is shown with a large body cavity in which are contained several 

 embryos. The largest of these is made up of about twelve cells. 

 The "Keimlager" is shown to be already established as a thickening 

 of the inner wall of the posterior end of the body. 



The digestive system, on the other hand, seems, so far as I can 

 make out from the figure, to consist of an undifi'erentiated mass of 

 cells. There is no apparent distinction between the primordium of 

 the gut and that of the pharynx, while no trace of the lumen of 

 either of these organs can be made out from the figure. 



In Diplodiscus temperatus the development of the redia takes 

 place in the manner which has been described by Rossbach for the 

 rediae of several species of Distomae. In the youngest rediae among 

 my material there was a series of cells constituting the primordium 

 of the gut which was becoming seperated from the surrounding 

 cells (Meristem cells of Schwarze) by a well defined space, the 

 beginning of the body cavity. At the anterior end of the redia the 

 pharynx was established and had already become hollowed out. The 

 body cavity was very small. The surrounding wall was thick on 

 all sides, especially at the posterior end of the body. There were 

 no embryos in the body cavity, nor indeed any cells (nuclei) in the 

 body wall which could with any certainty be distinguished as germ 

 cells at this stage in the development. 



