370 H. s. PRATT, 



but it may appear in the appendix as a very delicate, closely woven, 

 reticular layer in which cell-bounderies or nuclei do not appear. 



An interesting feature of the parenchyma is the extensive develop- 

 ment of submuscular or subcuticular cells. These cells are present 

 in the entire trunk of the worm, just beneath the superficial muscles, 

 being especially abundant near its hinder end : they are absent in the 

 appendix. They constitute a layer of more or less scattered cells, 

 usually oval in outline, and of various sizes, averaging 0.005 mm in 

 length; their nuclei are distinct and average 0.002 mm in diameter. 

 At the hinder end of the trunk these cells are sometimes so numerous 

 that they are closely pressed against one another so as to form two 

 or three layers (PI. 25, P'ig. 3 and PI. 26, Fig. 5). The submuscular 

 cells have a granular appearance and stain deeply with haematoxylin. 



I have detected no ducts connecting the submuscular cells with 

 the cuticula, but in so small a worm these might easily exist but be 

 impossible to see. Brandes (1892, p. 568) found such ducts very 

 distinctly present in an adult appendiculate Distome from the intestine 

 of Alosa ßnta and represents them in his fig. 6. In the portion of 

 the worm between the two suckers, the submuscular cells may present 

 a somewhat different appearance from those in the middle portions 

 of the body. They form here more or less irregular groups of pear- 

 shaped cells, the larger ends of which are directed posteriad: the 

 forward, attenuated ends are directed outward towards the cuticula; 

 but I could trace none into the cuticula, and could detect no openings 

 through it. These cells remind one strongly of the "Kopfdrüsen" so 

 often present in Trematodes. 



I have already said much concerning the submuscular cells in 

 other parts of this paper and have discussed the theories of some of 

 the authors who have mentioned them (p. 363). Leuckart (1886 b, 

 p. 188), Looss (1893, 1894, p. 131) and Nickerson (1894, p. 452) hold 

 them to be undifferentiated parenchymatous cells and Blochmann 

 (1896) considers them as forming the hypodermis of the worm. In 

 the opinion of the majority of hclniinthologists, however, they have a 

 glandular nature (see Braun, 1892, p. 595— 600; also Monticelli, 

 1892, 1893) and the very positive proof brought by Brandes (1892) 

 and Blochmann (1. c.) of ducts connecting them with the cuticula 

 seems to settle the matter beyond a reasonable doubt in favor of this 

 interpretation. And Looss, Nickerson and Blochmann, although 

 they do not call them gland-cells, attribute to them glandular functions, 

 in that, in their opinion, they secrete cuticular substance. All of 



