358 Mr. R. Hill's Contributions to the 



an egg-shell ; but the corresponding action in the same organ in 

 the Ray and the Shark goes no further than giving it a covering 

 of horn. " The egg, when thus completed, has somewhat the 

 shape of a pillow-case, with the four corners lengthened out into 

 long tendi-ils like cords," by which the egg is fastened to sea- 

 weeds, or branching corals, in the spots where they are deposited. 

 " A brittle egg-shell would soon be destroyed by the beating 

 of the waves, hence the necessity for the corneous envelope ; and 

 yet, how is the feeble embryo to escape from such a tough and 

 leather-like cradle V This obstacle has been overcome by a very 

 etficient expedient : the egg remains permanently open in two 

 places ; or, to carry out our humble simile, as Professor Jones, to 

 whom we are indebted for our details, very instructively observes*, 

 one side of the pillow-case is left unsewn in two places to receive 

 and eject water. The slightest pressure from within separates 

 the valvular lips of the openings, and no sooner has the little 

 Shark extricated itself from its confinement through one of the 

 slits, than the two sides close again so accurately, that the fissure 

 is not at all perceptible. In those Sharks which are viviparous, 

 that is, whose young are hatched in the oviduct prior to their 

 expulsion, this egg-shell is never formed, and the investments of 

 the foetus remain permanently membranous. 



In the Dictionary of Natural History, a work containing the 

 most recent information on the phsenomena of organic life, Bosc, 

 the author of the article on Rays, represents an intermediate de- 

 velopment in which the corneous egg is hatched within the parent, 

 and in which the young fish is expelled at the moment it bursts 

 the covering. There is some little obscurity in his narrative, but 

 it is plain that he not only insists on this intermediate process 

 of utero- gestation, but affirms that it varies in one and the same 

 Ray, and is sometimes a perfect hatching of the egg within the 

 parent, and sometimes a delivery of the foetus from the uterine 

 cavity, while it is still within the corneous envelope, and to be 

 hatched after extrusion in the surrounding waters, t give his 

 words : — 



" On observera sans doute avec surprise que je parle d'oeufs, 

 quoique j'aie deja dit que les Raies etoient vivipares; mais il 

 est difficile de s'exprimer autrement. Ce ne sont point de veri- 

 tables oeufs, ce sont des matrices oviformes que portent les 

 Raies. Quelque temps apres le premier accouplement, il sort de 

 lem* ovaire un de ces oeufs ou une de ces matrices, qui reste 

 attachee h la mere, et dans laquelle se developpe un foetus 

 jusqu'a I'epoque oii il est assez fort pour briser les enveloppes qui 

 le tiennent enferme, nager et se pourvoir de nourriture. Quel- 



* Lectiu-es ou the Animal Kingdom, bv Rymer Jones. Chap, xxvii. 

 sec. 582. 



