530 CRESSWELL SHEAREU. 



tions_, but only when the preparation has been pressed con- 

 siderably out of shape. In calling these clear spaces vacuoles 

 I do so through lack of a more suitable term; they are in all 

 probability filled with fluid, as in preserved material they 

 appear (as in fig. 13) as a series of narrow chinks, while 

 in the living state they are seen as large refractive spaces as 

 shown in fig. 7. Bohmig (1) in Triclada maricola shows 

 the excretory canals terminating in the basement membrane 

 beneath the epidermis, much as they do in Dinophilus. In 

 his fig. 19, PL 20, he shows this very clearly, and this figure 

 might very well do to illustrate the condition in Dinophilus. 

 lu this Triclad the epidermis also contains numerous clear 

 vacuoles, the Avails of which lie close against the terminal 

 point of the excretory canals. In spite of much time devoted 

 to this point in Dinophilus I have been quite unable to de- 

 termine anything further regarding the relationships of the 

 nephridial canals to the vacuoles or whether these vacuoles in 

 turn open on the exterior. This point is of some interest in 

 connection with Korschelt's (11) observation of the probable 

 presence of a fine system of anastomosing canals in the base- 

 ment membrane with which the nephridial canals may possibly 

 connect, although he could not succeed in D. apatris in 

 establishing any such connection. This is well shown in 

 Korschelt's (11) fig. 29, but no similar system is to be found 

 in the case of D. tseniatus. Korschelt pointsout the resem- 

 blance of this network to the system of canals into which the 

 ducts of the flame-cells of Polyclads open. These in turn 

 open on the exterior in two dorsal pores. By certain im- 

 proper focussing, however, of the muscle-strands which run 

 irregularly throughout the body, an appearance is obtained 

 of a series of anastomosing canals looking not unlike the pic- 

 ture shown in Korschelt's (11) fig. 29, and possibly it is this 

 Korschelt has taken for a system of canals ; that this network 

 is really made up of anastomosing muscle-fibres can readily 

 be determined by proper focussing. When it is considered 

 how notoriously difficult it is to see the external openings of 

 the ducts of the head-kidney in the Polygordius larva, the 



