ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 467 



cavity, which might be the stomach, surrounded by and communi- 

 cating with a number of convolutions or blind sacs. The matter 

 became clear only by giving up the idea that a strict corresi^ondence 

 with known forms was to be looked for." 



The stomach is not simple, but passes upwards into a number of 

 membranous pouches, which are attached to the roof of the disk-wall 

 to the inner points of the ovigerous lobes, and powerfully by ten 

 points which encircle the mouth. These last are brachial or inter- 

 brachial; immediately above the attachment of the latter there is a 

 much folded and fluted interbrachial stomach-pouch ; similar to its 

 attachments are those of the brachial pouches, and the whole arrange- 

 ment would divide the body-cavity into " ten radiating compartments 

 completely separated from each other, were it not that an open space 

 exists between the inner point of each attachment and the stomach- 

 sphincter." This space would seem to correspond to the inner 

 perihaemal canal, described by Ludwig as existing in the Ophiurida, 

 but it differs from it in not being closed. 



The ovaries are formed by deep, lobed, and contorted folds of the 

 lining membrane of the disk-wall on its floor, sides, and part of its 

 roof, so that there are no closed bursse, but the entire body-cavity, 

 with the exception of the just mentioned perihsemal ring, is also the 

 genital cavity. The eggs would appear to be impregnated in the 

 body-cavity. A description of a non-gravid Euryale is given, and it 

 is pointed out that the genital openings can be contracted or 

 expanded ; in the membrane lining the compartments the author 

 found fragments of " microscopic limework " comparable to those 

 found in the walls of the bursa of OpJiiura Icevis, and which, when 

 further developed, form the thin scales found in the walls of the 

 bursEe of Ophiotliamnus vicarius. 



Passing from the true Astrophytons, we find in Astrocnida isidis, 

 " a curious and quasi-intermediate structure." The stomach was, as 

 in Ophiurids, entirely free below, and there were no radiating lines 

 of attachment save the stout septum, which is also seen in Ophiurids. 

 The ovaries were arranged on the type of Astrophyton. Very similar 

 arrangements obtain in Astrogomphus. Ophiocreas oedipus is much 

 more Ophiurid. There is a distinct bursa, and the position of the 

 genital organs between the skin of the arm and the arm-bones is only 

 due to the smallness of the disk and body-cavity. 



Although we have, therefore, a series of stages, Mr. Lyman is of 

 opinion that Ophiocreas is not an intermediate but a synthetic form. 

 " It has the teeth of Euryale, the pleated stomach suggestive of 

 GorgonocepJialus, the genital bursa and ovarial tubes similar to, yet 

 not the same as those of Ophiurans in general, the arm-plates that 

 recall Ophiomyxa ; nay, one Astrophyton character, the adhesion of 

 the stomach to the disk-wall, is carried further than in Astrophyton 

 itself." 



Preliminary List of the known Genera and Species of Living 

 OpMuridse and Astrophytidse.* — Professor L. Lyman has added 



* 4to, Cambridge, U.S.A., 1880. 45 leaves, printed on one side only. 



