32 LUCEKNAUI.E AND THEIR ALLIES. 



pnrtition, and is so strongly convoluted as to appear like the end of a bundle of 



tlireads cut across. 



69 The chondrophii.'^ or chondrin-likc layer (PI. ii, fij. 19; I'l. i\i,fi(j. 37; PI. 

 IV, Ivis. 46, 47, 47% 5(), 51; PI. v,». 52, 54, 58, 60; PI. vi,.A>. 61-64; PI. vii, 

 fuj's. 82, 83; PI. x, fy/s. 127, 128; h to ¥) is restricted to the posterior parietes 

 "( fl<j. 37, fS) of the umbella, and to the peduncle. Compared with the chondromyo- 

 plax (65-68) it is much more rigid, dense, and inflexible, quite resilient and elastic, 

 and of a tough, jelly-like consistency. That it is dilatable and compressible is plain 

 enough when the corners of the octagonal umbella are prolonged into conical arm- 

 like projections, or when the peduncle shortens from half an inch to one-eighth of 

 an inch in length, and then regains its first proportions. Like the chondromyoplax, 

 it is nearly colorless, only sliglitly tinged with yellow or amber-color, and very 

 transparent. It is faced on the front by the lining wall {<jastroj^)liragma, *\ 75) of 

 the main cavity, except at the partitions, where it meets the chondromyoplax, as 

 was stated in a previous paragrapli (67), and is covered on the opposite side by the 

 outermost wall {eclophragiiia, % 63) of the posterior parietes of the umbella. The 

 massiveness and weiglit of this layer are unapproached by those of the chondro- 

 myoplax, and the only point at which the latter equals the former in thickness is 

 at the margin of the umbella, but yet even there we do not find the mean depth 

 of the chondrophys. In a rough estimate the latter might be set down at about 

 . three times the average thickness of the chondromyoplax. The general uniformity 

 in the depth of tlie chondrophys makes it much easier to measure than the other 

 layer, but still it lias some variations in thickness which are not to be passed by, 

 for more than one reason. In the first place they are variations in form as well 

 as diameter, and secondly they are connected with structural peculiarities. Tlrese 

 points will be developed as we proceed in our delineations of the outlines of the 

 different subdivisions of the layer. 



70. To begin with, we would state that the chondrophys is to all appearances a 

 double layer; that is to say, it is differentiated into two well-marked strata (c, c'), 

 which, however, do not seem to be separable, like other adjoining layers. Still 

 they have such an amount of diversity in cliaracter as to warrant us in taking 

 particular notice of each by itself In the first place, we will speak of them as if 

 they were one, under the term, llie chondrophys, inasmuch as they are inseparable; 

 the one being found wherever the other is to be met with. At all points of the 

 periphery of the umbella, except at the distal side of tlie bunches of tentacles {fig. 

 54, c), the chondropliys has an abruptly terminating, rounded-truncate edge {figs. 

 61, 62, etc., c) fitting into the concave-truncate border of the chondromyoplax 

 {% 65-68); whereas at the points excepted {figs. 54, 58, 60, c), which are eight in 

 number, the edge of the layer is bevelled off, so as to meet the chondromyoplax {¥) 

 at an oblique angle, the two overlapping each other as it were, the margin of the 

 former lying exterior to that of the latter. The manner in which a thin layer of 

 the opsomyoplax intervenes to prevent the actual contact of the borders of the 

 chondrophys and chondromyoplax is described in a previous paragraph (66). In 

 a l(,ngitudmal section of the body, in two different planes which meet at the axis, 

 namely, one runnmg through an anchor and along a partition, and one of the 



