LUCERNARIyE AND 'I'll Kill ALLIES. 91 



tions in all regions of the body in which it is destined to develop. In the tenta- 

 cles [fif/. 48, i') it is on the average as thit'k as the outer or inner walls, and is 

 very delicately striated. The same may be said in regard to the anchors (^figs. 82, 

 83, b). In the umbella it is variable in thickness; in the circumoral area (./'(/. 

 53, i) it is fully twice as thick as either the outer or inner wall, but scarcely more 

 than half the depth that obtains in the proboscis (Jy). Throughout, however, it is 

 much more heavily striated than in the tentacles and anchors. In absolute thick- 

 ness this layer has in the anchors from two to two and a half times more depth 

 than in the tentacles and circumoral area. 



186. The Choudroplnjs at the umbella exhibits a higher number of subdivisions 

 than we have detected at subsequent periods. Of the three (,/?;/•''• 82, 83, c, c\ &) 

 now visible, the innermost, thin substratum (c') was not observed in the last phase. 

 This is the one which is conspicuous throughout the remainder of the existence of 

 the animal, while the outermost, and by far the thinnest one (c'), seems subse- 

 quently to lose its character as a separate subdivision. The latter in its earliest 

 phase was very conspicuous, but in the present state it is quite faint, and nearly 

 escaped our attention when the chondrophys was under the microscope. It is appa- 

 rently quite homogeneous in substance, of a light yellow color, and about as thick 

 as the outer, aboral wall. It is barely possible that it exists in mature individuals, 

 but is so excessively faint as to require a special effort to find it. The main bulk, 

 or middle portion (r) of the chondrophys, is enormously thick ; equalling at least four 

 times the diameter of the shaft of the oldest tentacles. Unlike the two thinner 

 subdivisions, it is strongly striated in transverse section, and thickly peneti'ated by 

 fibrous prolongations, which originate in the two outer subdivisions (see ^ 197, A). 

 Its marginal termination at the bases of the anchors has nothing of the abruptness 

 of the mature form, but, rather, tapers off rapidly to a sharp edge where the mus- 

 cular layer of the anchors intervenes (at Ic^) between it and the chondromyo- 

 plax (Jr). 



18T. The Opsophrarima, or circumoral {fuj. 53, n) and proboscidal («^) outer 

 wall, differs but little, if any, in thickness from that of the mature individual. Its 

 proportion on the anchors {figs. 82, 83, ir) has already been described (^ ITO), 

 when the development of these organs was under consideration (§ 22). The ecto- 

 fhiagma {figs. 82, 83,/), or outer Avail of the aboral side, also closely approxi- 

 mates that of the full grown body in character and proportion. 



188. The Gasfrojjhi-agma, or innermost wall, at this age may be traced, with 

 great facility, into its direct continuation with the opsophragma at the mouth {fig. 

 53, i') of the proboscis. It is there very thick, and continues so to the base of the 

 proboscis, where it rapidly thins out and loses nearly two-thirds its depth as it 

 passes along the circumoral area (/) to the periphery of tlie umbellar chambers. 

 Its rapid thickening as it approaches and enters the anchors {figx. 82, S3, /') has 

 already been touched upon (^[ 170) in the history of the development of the latter 

 organs, and needs no further notice here, except to contrast it, at the present age, 

 with its proportions and absolute thickness in tlie mature animal {fig. 47, «'). It 

 will be seen, by comparing the illustrations of the first (.//.'/• ^3, «') and of tlie last 

 {fig. 47, t'), that, in order to attain to the proportions of the latter, this wall must 



