92 DR. THOMAS ALCOCK ON THE 



The animal was seen to be fish-shaped; and the ridge along 

 the back and tail was distinct. On each side of the head 

 were two thick projecting processes, and on the right side 

 a third, small one, in front of the two. The animal fre- 

 quently bent itself together so that the head and tail met, 

 and then allowed itself to straighten again as much as the 

 confinement of the egg-membrane would allow. 



Plate III. 



I have daily compared the ovum in the watch-glass, 

 from which all the drawings have been made, with a large 

 number of others kept in a basin, and have found the one I 

 selected to show a fair average of the rate of development. 

 Many tadpoles in the basin have now, on the 13th day, 

 escaped from the egg-capsule; but there are others in 

 every stage of development, and in the centre of the mass 

 are some ova which, though living, still retain their 

 rounded form. 



13. The body was much compressed and decidedly fish- 

 shaped. The external gills were beginning to bud out in 

 the form of two undivided processes on each side of the 

 back of the head. The animal frequently curled up its 

 tail and body close to its head and then relaxed itself. 



14. The body was perfectly fish-shaped ; and there was 

 a projection under the throat, seen when the animal turned 

 about, but not represented in the drawing. The external 

 gills were large and branched, and were two on each side ; 

 on the right side the anterior had two, and the posterior 

 three divisions. 



14 (2). A second drawing was made six hours later, 

 when the gills were found to be larger ; and on the leftside 

 the secondary processes were arranged comb-like, or all on 

 one side of the main stem : they were four in number on 

 the anterior, and five on the posterior. 



