St. Andrews Marine Laboratory . 43 



However, as a rule mouthless marine animals are provided 

 with certain definite modes of sustenance other than the 

 mere imbibition of sea-water. Thus larval fishes devoid of 

 a mouth have a yolk-sac, and protoplasmic animals either 

 surround the food-particles with their bodies or place them- 

 selves in actual contact with them. The Hydromedusre are 

 generally somewhat voracious forms, even the smallest 

 attacking animals much larger and higher in the scale than 

 themselves. It is possible therefore that such mouthless 

 Medusae may, by contracting the disk, fold themselves over 

 prey of various kinds, and thus directly absorb nourishment 

 through the ectoderm. They certainly show remarkable 

 eagerness and mobility in feeding. No species is more con- 

 spicuous in this respect than Lizzia octopunctata, which will 

 permit itself to be dragged behind a Sagitta with the umbrella 

 everted rather than loosen its hold. Again, L. Agassiz has 

 seen half an Idyia (Berae) close over a small Bvlina and 

 digest it, the cut edges overlapping its prey *. He seemed 

 to think, indeed, that mutilated Discophora fared better in 

 confinement than entire specimens. 



The foregoing condition (in which the Medusae are deprived 

 of mouth and stomach) is the opposite of that described by 

 Arnold Lang in Gastroblasta liajfaeli^, in which there are 

 several stomachs and a variable number of apparently 

 irregular tentacles and radial canals. None showed a truly 

 radial arrangement. Many presented undulations in the out- 

 line and were ellipsoidal, indicating that they were in a state 

 of division. They had sprung from others by the same 

 method, the division commencing in each case at the margin, 

 and it is probable that from very small parts an entire Medusa 

 may be developed. If these Medusa? possess radial larva? 

 like Eucope, and propagate themselves by successive right 

 angular divisions, we necessarily get a series of apparently 

 irregular stages such as those described. 



2. On the Occurrence of the Ctenophores throughout 

 the Year. 



Louis Agassiz considered the Ctenophores in general as 

 annual animals, laying their eggs in the water in the autumn 

 and then dying, the young brood making its appearance in 

 the spring. He watched them on the shores of Massachu- 



* Contrib. Nat. Hist. United States, vol. iii. p. 173. 

 t Jenaische Zeitschr. vol. xix. (1866). For this reference I am in- 

 debted to Dr. Sckarff, of the Museum of Science and Art, Dublin. 



