356 CARL VOGT. 



stem is attached is designated the posterior, and the opposite the 

 anterior. It must be understood, however, that these terms do 

 not express any homological relation, but are simply topo- 

 graphic, employed to facilitate the comprehension of the figures 

 and descriptions. 



The skill of Loxosoma is composed throughout of two ele- 

 ments, a homogeneous and transparent cuticle and a hypodermic 

 layer, made up of granulous cells, associated at certain points 

 with muscular fibres, more or less pronounced. 



The cuticle [a) is structureless ; it is rather thick over the 

 surface of the body proper and of the stem, but becomes attenu- 

 ated over the tentacular region, though easily recognisable 

 throughout. It is clearly elastic to a certain extent, and yields 

 readily to the pressure of the internal organs, bulging out over 

 the eggs and visibly throwing itself into folds under the influence 

 of the muscular contractions. 



The hypodermic layer {b), closely united to the cuticle, of 

 which it is undoubtedly the matrix, is composed as a rule of a 

 single stratum of very granulous cells, irregularly shaped, which 

 projects on the inner side, and in which minute nuclei, differing 

 but slightly from the granular protoplasm, may be detected with 

 difficulty. This layer is coextensive with the cuticle, and pre- 

 serves, for the most part, an uniform thickness. ^ It is continued 

 over the tentacles and the stem ; but in these two cases it com- 

 bines with other elements, which will be noticed hereafter. 



The author has no doubt that the rudiments of the generative 

 organs and their contents are derived from the hypodermic cells. 

 No histological element is met with, apart from tliese cells, that 

 could contribute to their formation. The reproductive organs of 

 Loxosoma^ to employ the recognised phraseology, are therefore a 

 product of the ectoderm. 



The skin, speaking generally, over the whole extent of the 

 body presents the appearance of an uniform, smooth layer, with 

 a look of rigidity. At a definite point, however, between the 

 posterior margin of the tentacular crown and the anterior extremity 

 of the stomach there occur a few superficial folds or creases (r), 

 which are palmate in form and placed transversely. They seem to 

 depend on the position of the thick anterior lip-like appendage 

 which guards the entrance to the oesophagus, as we shall see 

 hereafter, making their appearance when it is closed and at rest, 

 and disappearing when it is raised to allow of the entrance of 

 food. 



' One or two exceptions are noted, but they appear to have no special 

 significance . — Transl. 



