44 Unusual Modes of 



gills had disappeared, but were replaced by internal ones, which 

 were arranged as. usual on three hyoid arches. The development 

 of the lungs had commenced, and these were represented by a 

 slender conical mass of cells, but not permeable to air. The 

 mouth was provided with finely denticulated horny jaws, and the 

 intestinal canal was shorter and less spirally convoluted than in 

 ordinary larvae of frogs and toads. The stomach was not so much 

 developed as to be distinguished from the rest of the intestine ; 

 but this last, after passing the liver, was somewhat dilated, and 

 contained, as was shown by the microscope, large quantities of 

 yolk cells which had not been absorbed and which were adherent 

 to its walls. 



We have here then a larva, in all of the details of its structure, 

 especially in the existence of gills and o f a flattened tail, adapted 

 to aquatic locomotion and respiration, yet passing a portion of its 

 time at least on the back of its parent and at a distance from the 

 water. 



I was not able to ascertain whether the eggs were primarily de- 

 posited in the water or not, but it is well known to some of the 

 colonists that after the larvae have reached a certain degree of de- 

 velopment they are carried about in the manner just described 

 and they do not know them under any other circumstances. The 

 existence of yolk cells in the intestine, shows that for a period at 

 least they may have from these a supply of nutriment. Bat after 

 this is exhausted, and it appeared to be nearly so in those which 

 I have dissected, how do tbey obtain their food ? In the absence 

 of limbs adapted to terrestrial locomotion can they leave the body 

 of the parent ? and if they cannot, do they, as in the case of Pipa 

 and probably in Notodelphys, depend upon a secretion from her ? 



Among Fishes, as far as at present known, the external condi- 

 tions under which the eggs are developed are more varied than 

 in any other class of Vertebrates. There are scarce any known 

 conditions of the higher classes to which there are not analogies 

 at least in the class of fishes. Besides the ordinary mode of de- 

 positing eggs upon the bottoms, some of the Salmonidse, like the 

 turtles, bury their eggs, the Lampreys (Petromxjzon)^ the Breams, 

 (Fomotis), the Hassars (Callicthys), the Stickle-backs, [Gaster- 

 ostei), &c., build more or less complete nests. Among some of 

 the Pipe Fishes, (Syngnathidce), the eggs and subsequently the 

 young, are carried in a pouch analogous to that of the opossums 

 and other marsupial animals, and among some of the Sharks 



