No. 6. — The Stomach atid Genital Organs of Astrophytidce. 

 By Theodore Lyman. 



(Published by Permission of the Lords Commissioners of the Treasury, and of the 

 Hon. C. P. Patterson, Supt. U. S. Coast Survey. ) 



In typical Ophiurans, the mouth, just above the teeth, opens by a 

 round contractile aperture (the stomach-sphincter) into a large flat- 

 tened sack (the stomach), which spreads over the bases of the arms and 

 into the interbrachial spaces. This stomach is commonly separated by 

 a greater or less space from the outer disk-wall, to which it is suspended 

 by delicate threads. Although sometimes a little wrinkled or pleated, 

 it is usually simple, and destitute of pouches, convolutions, or coecal 

 appendages. Such is the form that runs through the whole series of true 

 Ophiurans, so far as I know them, not excepting the archaic Ophiomu- 

 sium. Between the stomach and the disk-wall lie the reproductive or- 

 gans. Proceeding inward from a genital opening there is, first, an 

 elongated bag (bursa, Ludwig), which is a fold or bubble of the lining 

 membrane, and which, by minute holes, communicates with other little 

 bags, simple or contorted, the egg- or spermatozoa-bearing tubes {ovarial 

 Schlduche). It will be noted that these bursse, as Ludwig has shown,* 

 are closed sacks, having no conununication with the body-cavity, and in 

 this respect hold the same relation to the genital openings that the 

 stomach holds to the mouth. 



A similar structure might reasonably have been looked for among the 

 Astrophytons, which, despite their curiously branching arms having 

 special joints and a peculiar covering, are, especially in the young 

 stage, very closely allied to the Ophiurans. Indeed Ophiuridae are in 

 some sort connected with Astrophytidse, albeit in no straight or un- 

 broken line, by such genera as Ophiomyxa, Ophiochondrus, Hemieuryale, 

 Astroschema, Astrogomphus, and Astrocnida. 



When, therefore, I made a first section of a fine Gorgonocephalus 

 Pourtalesii, brought back by the " Challenger," and whose swollen disk 

 indicated a gravid individual, I expected to find a general arrangement 

 of organs quite similar to that already known in such genera as Ophio- 



* Hubert Ludwig : Beitrage zur Anatomie der Ophiuren. Zeitschr. fiir Wissen- 

 schaftl. Zoologie, Bd. XXXL, 1878. 

 VOL. VIII. — NO. 6. 



