SANGUINICOLA 235 



or ' Hakchen ' described by Plehn, except posterioriy where the 

 edges turn mediad in order to unite (PI. 1 8, fig. 1 , sp). The spine- 

 lets are distinct rods of the form shown in fig. 9, and are ahiiost 

 entirely embedded in the subcuticula and parenchyma save 

 for their outer extremities, which project slightly. These 

 spinelets attain a maximum length of about 27 microns, and 

 they are apparently identical in nature with the chitinous spines 

 found in the skin of many Malacocotylea. 



For the reason to be supplied later when describing the genital 

 apparatus, I shall consider the side of the body bearing the 

 furrow as the dorsal surface, from which it follows that the 

 genital openings are situated, as in most Turbellaria and 

 Trematoda, on the ventral surface. 



In general shape (PI. 18, fig. 1) the Sudan Sanguinicola 

 resembles the Sanguinicola described by Plehn. As Plehn 

 describes, and as is evident even in preserved material, the 

 body is highly contractile and in much contracted specimens 

 may be a broad oval in outline. 



As regards the internal organization, the two chief systems 

 of organs to be described are the gut and the genital apparatus ; 

 I have nothing to add to Plehn's description of the nervous and 

 excretory systems and the general histology. 



The gut, as shown in figs. 1, 4, 5, 6, is in a much reduced 

 condition as compared with the gut in most Turbellaria and 

 Trematoda ; but that it is a gut and not a ' frontal gland ' is 

 shown not only by the presence of a well-marked muscular 

 sucking pharynx (ph) and by the non-glandular character of 

 the w^all of the gut sac (gs), but also by the occasional presence 

 of distinct blood-corpuscles in its lumen (seen in two of my 

 specimens). The anterior mouth-opening (m) is, as in all 



be detected by careful focusing ; also in young specimens the spinelets 

 are smaller than in full-grown forms and in very young forms are absent. 

 I hardly like to suggest that a conjunction of these two conditions is 

 responsible for the description of the S. inermis of Dr. Plehn, but it 

 appears to me that the suggestion might be applicable. The difference 

 of size between the two species S. armata and S. inermis quoted 

 by Liihe is of no specific value. 



