84 



LUCERNARIJi AND THEIR ALLIES. 



iii-r;dvv in both respects, since it almost encircles the proximal as well as the distal 

 antl lateral faces, and also has such a strong development of its depth as to present 

 a prominent hump on the distal side. We ought to mention, also, that the chon- 

 dromyoplax (b-) is a strongly marked layer in the coUetocystic mass. 



108. Keturning, now, to the specimen from which we obtained the youngest 

 anchors, we tind, in a normal condition, {Jig. 32) a phase slightly advanced beyond 

 the last; differing principally in the increased relative shortness of the shaft, 

 tendin", as we shall see hereafter, to sink the globose tip into the coUetocystic pad 

 (oc')- There is no diminution, however, in the intensity of the tentacle character- 

 istic ; in fact, we might justly say that it is rather increased in some respects, for 

 instance, by tlie greater sharpness of the line of demarcation between the shaft 

 and the spheroidal tip, and particularly by the appearance of the narrow, elastic 

 band at that point, so eminently conspicuous in tentacles fiir advanced in develop- 

 ment. The physiognomy of the coUetocystic mass does not vary from the youngest 

 example, as regards its histological elements, but, as for its proportions as a whole, 

 there is a sufficiently marked change to render a comparison of it with a fully- 

 developed anchor facile enough to satisfy the most exacting criterion. Already 

 the terminal portion of the shaft and the globose tip have the appearance of being 

 ai)pendages of the coUetocystic pad, rather than the reverse. The dominant feature 

 of tlie anchor is rapidly approaching the condition when it is the only one to be 

 seen without a special search. We think this will be clear enougli to any one 

 who will take the trouble to glance over the following figures {Jhjs. 81, 82, 83, 26, 

 27, 25), which are yet to be used to illustrate c/ur subject. We have yet to mention 

 one oilier feature of progress in the case before us, and that is, the strong bulge 

 (////. 32, oc'^^) of tlie proximal face of the shaft, opposite the area covered by tlie 

 pad. It is not yet encroached upon by the coUetocystic mass, but yet it may be 

 forced out into a prominence by the gradual enlargement of the lateral extent and 

 depth of that mass, rather than by any inherent property. The cavity of this 

 organ, however, would seem to militate in favor of the latter view, for we learn, 

 upon close scrutiny, that the lining wall—ffast)-02)Jira</ma — bulges and thickens a 

 little also, in the same region, so as to trend parallel with the outer wall. This 

 could hardly be produced by any influence that the coUetocystic mass might bring 

 to bear, especially as it is the initiatory step in the formation of the larger freed 

 chamber of the full grown organ. The chondromyoplax plays a much more con- 

 spicuous part here than in the oldest tentacles of this individual, occujiying at 

 lenst three-fiftlis of the depth of all the combined layers. 



1G9. In order to make the developmental process of the anchors as clear as 

 possible, it seems advisable to describe it in a continued succession of sketches, 

 and we shall, therefore, draw into the limits of this section all the phases that we 

 possess, in the form of illustrations. The next one that we shall take up for con- 

 sideration (figs. 81, 82, 83) has lost a large part of the shaft of the tentacular 

 form, and tlie globose tip (oc') stands out like a high knob on the oblique face of 

 the coUetocystic pad (ocl) It belongs to a specimen which measures slightly 

 less than one-fifth of an inch across the umbella (fig. 84). The pad (oc') itself 

 extends, on the distal side, downward to the base of the ori-anal shaft, as in the 



