40 LUCERNAIU^ AND THEIR ALLIES. 



wherever it passes beyond that, although not dissolving its continuity, it becomes 

 another subdivision of the system, for instance, that of the tentacles, or ot the 

 anchors. At the ancliors its junction with tliem is indicated by the prolongation 

 of the ridges of the marginal band (m') into the stem of these organs (at m'}, and 

 may be readily traced by a surface examination; but since all the ridges fail in the 

 region of the tentacles, the relation of this layer to its continuation in the latter 

 organs can only be determined by au actual section of the parietes thereabout, thus 

 displaying a profile of its thickness, and the course it takes in making the connection. 



85. The (jastromyoplax, or oomyoplax has already received all the attention 

 that is necessary to define its position and connections in reference to its general 

 surroundings, and, as we have said in a preceding paragraph (74), since it is wholly 

 devoted to^he reproductive organs and their appendages, we shall defer a special 

 description of it until those organs come under particular examination ; but, inas- 

 much as it is a branch of the great subdivision which converges at the proximal 

 ends of the partitions, and concentrates in the peduncular cords, it is eminently 

 proper to repeat here what has been said in reference to its mode of junction with 

 the latter, and perhaps to add some other matters of interest. Contrasted with the 

 opsomyoplax it is very tliin, and might readily escape the eye of the observer, 

 unless his attention were drawn to it by the activity and evident muscularity of the 

 digitiform bodies. Between the necks of the genital saccules it is thickest; it 

 thins very sensibly as it passes into the latter and into their appendages, and is a 

 mere film where it folds over the proximal ends of the partitions and joins the great 

 cords of the peduncle. (See ^f 76.) 



86. In the tentacles the muscular system {figs. 43, 54, 90, 91) ceases to be a 

 continuous layer, but still it retains the same relations to the opsophragma and 

 the chondromyoplax that it had in the umbella. The difference consists in this : 

 instead of being a distinct stratum, it is, as it were, split into a large number of 

 threads which are grouped in bundles {fig. 90, tir) of two, three, or four, more or 

 less mutually overlying ; the bundles being separated from each other by varying 

 intervals, and trending lengthwise of the tentacles. This accounts for the longi- 

 tudinally ribbed appearance {figs. 43, 54) of these prehensile organs when viewed 

 with a low power. 



87. The anchors (coUctocystophores, § 13) possess a modification of the muscular 

 layer identical with tliat in the tentacles, which may be as conveniently traced in 

 their youngest stages of development, before their tentacular nature is disguised; 

 but, in consequence of the great changes which take place, by the thickening of 

 the outer wall and the development, in it of the adhesive vesicles (colletocysts, § 27), 

 the full-grown organs present great difficulties in the way of tracing the course of 

 the bundles of muscular threads. We have succeeded in doing so, notwithstanding, 

 and shall describe the results in detail in the special paragraphs (§ 13) on these 

 oi-ans, since the relations of the fibres in question cannot be properly understood 

 without a knowledge of the peculiar conformation of the several strata which con- 

 stiuite the anchors. This reason will apply with equal force to the tentacles. 



88. he mnscnlar cords {figs. 19, 46, 47', 50, 52, 113, 117, r to r^) of the 

 peduncle necessarily demand our notice here, as a part of a general system, although 



