375 



The eggs, however, are not loose as in the oviducts of birds, but are 

 grouped together to the number of three, four, or five, in membra- 

 nous bags, containing a transparent jelly, in which the young fish 

 swims about after it is formed, with the yolk attached to its belly by 

 a long chord, consisting of blood-vessels. If the bag be torn and 

 the fish taken out and put into water with its yolk attached to it, it 

 swims about ; but if the vessels of the chord are wounded, it dies im- 

 mediately. 



The author is of opinion that many of the shark tribe have this 

 mode of hatching ; but with respect to the large shark between the 

 tropics, the fact has been already observed by Dr. Patrick Russell, 

 who in oneinstance found twenty-one youngones in the right oviduct, 

 and twenty in the left. 



The gelatinous liquor surrounding the ova being found to differ in 

 its properties from their animal jellies, excepting that with which the 

 ova of frogs are surrounded, Mr. H. procured some frogs that he 

 might watch the formation of their jelly, and examine its properties. 

 No change was observed to take place in their ovaria through the 

 winter, but on the 10th of February when a portion of oviduct was 

 immersed in water at 80, it swelled to double its size, and even larger 

 when the water was warmer. On the 25th of February a portion of 

 oviduct, only two or three inches long, being put into water at 120, 

 swelled to such a mass of transparent jelly as filled a half pint tum- 

 bler. This substance resembled what is occasionally found on the 

 ground, and on the branches of trees, and is called star-shot jelly ; 

 which by Pennant has been supposed to be brought into that state in 

 the stomachs of herons and of other birds that feed on frogs, and 

 then rejected by vomiting. 



Mr. Brande was consequently requested to make a comparative 

 examination of the jelly from the shark, of the jelly obtained from 

 the oviducts of frogs, and of star-shot jelly, procured from Lincoln- 

 shire ; and he found them to agree perfectly in their properties. 



When dried they become brittle, but when put into water, they 

 expand again to their original bulk, even although the heat of boiling 

 water has been applied for drying them. Water does not appear to 

 dissolve any portion of them even by boiling; they dissolve, however, 

 by acids or by alkalies. As none of the solutions are precipitated by 

 tannin, the substance distinctly differs from gelatin; and as it is not 

 coagulated by heat, by acids, by alcohol, or by electricity, it differs 

 equally from albumen, and must be considered as of a peculiar nature 

 not yet described. 



The subsequent part of Mr. Home's communication relates to the 

 provisions for supplying the foetus of different animals with air. 



The ova of many fish are laid as near the sources of rivers as they 

 can be, for the sake of the greater proportion of air contained in the 

 water. Others are attached to plants which assist in supplying them 

 with oxygen. The ova of sharks and of skates, which have their 

 coats too strong to be penetrated by sea-water, have apertures at 

 each end for its admission and escape. 



