■RKJIARKABLK SPECIES OF ECIIIUROIDS. 7 



them, it is with great difficulty that their presence can be 

 ascertained. Very much easier is it to observe tliem on sections 

 cutting tliem in an ol^lique direction, as, f. i., on a jiaratangential 

 section such as shown in fig. 8 {cm., l.m.). Seen on such 

 sections the continuity of both systems as layers is interrupted 

 by the presence of a number of variously sized oblong sj)aces 

 (/. s., fig. 8) that interpose between the fibers. The spaces are 

 elongate in the direction of the course of the fibers constituting 

 the layer. A series of uuclei arranged in a line marks the 

 boundary of the spaces, presenting an appearance as if the latter 

 were provided with an endothelial lining. As a matter of fact, 

 however, I believe the said nuclei belong to the connective-tissue 

 and were apparently brought into the above arrangement by the 

 pressure, as it were, of the spaces in question. These spaces 

 themselves are evidently nothing else than direct continuations 

 of the lacunae of the trabecular layer. 



The trabecular layer {t.l, figs. 9-11, 18) forms a voluminous 

 part in the entire thickness of the body-wall. Especially thick 

 is it on the sides where the body-wall is thickest. It may be 

 said that the layer consists of irregularly branching and anasto- 

 mosing trabecule and of a system of irregular lacunar spaces 

 that surround the trabeculœ. These seem to be essentially com- 

 posed of fine, reticular and loosely bundled fibers — connective- 

 tissue fibers — amongst which at certain intervals are seen the 

 nuclei of the tissue. The trabeculaî contain, besides, a certain 

 number of other fibers which, from their appearance, may be 

 called muscular (m./., fig. 0). The lacunar spaces in the layer 

 contain a lymph-like fluid that bathes the trabecule on all sides. 

 The fluid can be deeply stained with hematoxylin. It is probably 

 of a nutritious nature. 



