58 



ova are deposited on the external surface of the male parent, 

 ■where they possess all the benefits of free exposure, with a 

 sufficient portion of animal heat. The eggs of the Crab and 

 Lobster possess the same advantage, chiefly perhaps for the 

 sake of a frequent change of water, which is equivalent to a 

 flowing stream, the health of this class of creatures mater- 

 ially depending on the frequent renewal of the purest water, 

 but in a less degree also, for the sake of vital heat and 

 protection. They are therefore suspended to the body for 

 a long period, but are developed very quickly after they are 

 shed. 



In our present state of knowledge we can only wonder at 

 the variety of nature, by which it becomes the duty of the 

 male Syngnathus Acus to carry about enclosed in cells, be- 

 neath the caudal portion of the body, the eggs, and after- 

 wards the young; which take refuge there even after their 

 first exclusion; and that too, it would seem, not only at the 

 approach of danger, but for the sake of warmth and shelter. 

 This curious fact displays an analogy to the Kanguroo and 

 other marsupial animals, and finds a correspondence in the 

 mysis, a genus of shrimps common on our coasts; of which 

 one sex, carries about under its thorax, supported by an or- 

 ganization fitted to the purpose, the eggs and afterwards the 

 young, until they are able to shift for themselves. 



It appears that in what are termed viviparous fishes, no 

 direct communication of nourishment takes place between the 

 parent and offspring; and the remark of Gesner, that one 

 species of Shark is attached by a funis to its mother, has not 

 been supported by further testimony. It follows then, that 

 the quantity of nutriment originally enclosed in the egg 

 (usually a yolk and white, though these are not clearly dis- 

 tinguished by their colour in most marine animals) is exactly 

 fitted to the duration of the creature's fastal life, the whole 

 being absorbed into the body just at the moment of birth. 

 But there is reason to believe also, that in some species the 

 egg increases in size after exclusion, by an endosmodic ab- 

 sorption from the surrounding fluid : thus allowing room for 

 a greater increase of bulk, as well as providing a more diluted 

 nourishment to the embryo; and at the same time affording 

 an explanation of the fact, of the disproportionate size of the 

 newly excluded fish, compared with the deposited pea. 



A curious part of our subject is the frequent occurrence of 

 hermaphroditism in fishes ; a circumstance that displays itself 

 most frequently in the presence of a melt on one side of the 

 body, and a roe on the other; but I have seen an example in 

 the Mackarel, where a single lobe of roc lay between the two 

 usual lobes of melt. Whether fishes thus circumstanced are 

 capable of self propagation has not been ascertained, and the 



