[67] NOTES ON ENTOZOA OF MARINE FISHES. 785 



Structure of head and neck. — A section was made through the anterior 

 disk and carried back through the cervical mass into the anterior part 

 of the body. The latter enters the cervical mass from behind and at 

 first seems to be independent of it, being surrounded by the posterior 

 frill-like lobes of that organ within the cervical mass. The anterior part 

 of the body is seen to enlarge mto a kiud of central core, which in part, 

 at least, is continuous with the anterior disk, and into which it expands. 



The cervical mass while in great measure free from the anterior disk 

 and the inner core, is in reality intimately connected with both. The 

 disk is composed of very densely compacted muscular fibers uear the 

 exterior, with a somewhat looser texture in the central portions. The 

 dense tissue of the exterior can be traced back into the core or central 

 part of the cervex. A line of demarkation can be distinguished be- 

 tween the disk and the anterior part of the core, on the one hand, and 

 the crisp folds of the cervex on the other, while at the posterior part of 

 the core no such line of demarkation exists between it and the cervex. 

 Longitudinal muscular fibers from the anterior part of the body con- 

 tinue into the central core, thence some radiate into the frill-like folds 

 of the cervex, while others continue into the anterior disk, where they 

 diverge in all directions to form the latter organ. Branches of the 

 water- vascular system were observed in the anterior disk, the central 

 core, and the inflated folds of the cervex. A section of the latter organ 

 resembles a cluster of racemose glands radiating from a central core. 

 Bundles of muscular fibers radiate from the central core to the deeply 

 and crisply folded exterior. The tissues of this part are very loose and 

 open, and the external folds of the surface are thin and transparent. 

 Although no movement was observed in this organ in the living worm, 

 it is evident from the presence, in considerable quantity, of muscular 

 fibers and the voluminously folded surface as revealed in sections, that 

 it is capable of great change of form. Its loose and delicate structure 

 shows it to be, at least histologically, homologous with the crimped aud 

 folded bothria of many of the Phyllobothrinw. The organ doubtless 

 serves an analogous purpose to the bothria of such forms. Its structure 

 shows that it is pre-eminently adapted for absorption. On the other 

 hand the structure of the anterior disk as clearly shows it to be an 

 organ whose chief use is to enable the parasite to adhere to its host. 



Musculature of body. — The anterior part of the body, immediately be- 

 hind the head, as shown in transverse sections, consists of a thick outer 

 layer which appears to be composed, for the most part, of radiating 

 fibers. This layer is succeded within by a narrow layer of circular 

 fibers. The latter surrounds an elliptical central space in which there 

 are longitudinal fibers, most abundant on its outer circumference ad- 

 jacent to the circular layer. In this central space the cut ends of four 

 aquiferous vessels are seen. These lie in pairs toward the margins. 

 Each pair comprises a larger and a smaller vessel, lying near together, 

 the smaller being the one which is nearer the margin. 

 H. Mis. 133—50 



