INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 963 



Comatulfc, there being no ambulacral plates, sucli as occur in all 

 known Stellerida. 



M. Perricr remarks that the contrast between the arms and the 

 disk, the probable absence of genital glands from the arms, and the 

 absence of stomachal cfeca, would seem to ajiproximate this form to 

 the Ophiurida, just as the structure of the arms would ally it to 

 the Comatulie ; but although in the abuormal characters above cited, 

 and especially the want of ambulacral and buccal plates, it differs 

 from all known Stellerida, the evidence of the pedicellarife leads him 

 to class it in that group, as forming an aberrant family of the Aste- 

 riadas, in the neighbourhood of the genera Lahidiaster, Pedieellaster, 

 and Brisimja, which also possesses only two rows of ambulacral 

 tubes. 



M. Perrier names this singular starfish Uymcnodiscus Arjassizii. 

 It was obtained within sight of the island of JJomiuica, from depths 

 of 321 and 450 fathoms. 



Formation of the Egg-coverings in Antedon rosacea.* — Dr. 

 Ludwig states that a short time before the extrusion of the ovum there 

 is to be noted, on the aboral surface of the pinnulfe, a small circular 

 projection, distinguishable by its whitish colour ; if we open a piuuula 

 at tliis stage and examine the ova we find a special disposition of their 

 surface. The whole egg ajipears to be invested by a network, the 

 bars of which are darker than the circular meshes. Further observa- 

 tion shows that this network owes its origin to a special development 

 of the investment of the ovarian cell and of the cell itself, for tlie 

 investment is, on its inner surface, villous, and the villi jiroject into 

 the yolk-sj)heres of the egg, so that the rounded clear spaces, already 

 noted, are merely the ojitical section of these villi. When the eggs 

 have been for some time subjected to the action of sea-water we find 

 that the surface of the egg has become plane, and has got itself in- 

 vested by a thick shell. 



Ccelenterata. 



The Ctenophora.f — This paper by Richard Hertwig occupies 135 

 pages, and is illustrated by seven plates. The more general results to 

 which his investigations have led him are the following : — 



Structure of the Generative Organs. — Do these arise from the ecto- 

 dermal or from the endodermal layer ? Among the later writers wo 

 find Glaus on the one side and Chun on tlie other. Hertwig agrees 

 with Claus in regarding them as having an ectodermal origin. Tho 

 epithelium of the surface of the body projects into tho ctenoiihoral 

 vessels in the form of small saccules, which project into the gelatinous 

 layer, and reach as far as the endodermal epithelium of the vessels. 

 Hero they broaden out and form two epithelial layers, which are 

 separated by a cleft, the genital sinus. The layer which bounds tho 

 endodermal epithelium forms tlie generative products. As thiro are 

 uo blood-vessels, the tissues wliieh reijuire a rit-h supply of nutriment 

 are developed in close connection with those branches of the enteric 



♦ ' Znol. Anzcig.,' iii. (1880) p. 470. 



t 'Jon. Zeitschr. Naturw.,' xiv. (1880) j). :U3. 



