106 DR. THOMAS ALCOCK ON THE 



55 (4) . A drawing was made of the right gill as seen 

 under the microscope with the two-inch object-glass. 



56. A score of tadpoles were taken from among the 

 dead leaves in the pond at one sweep of the dredge. The 

 largest was selected for examination. A very strong 

 constant current came ont through the outlet of the gill- 

 chambers; but no current was seen entering the nostrils. 

 The mouth was constantly opened and closed with an 

 action like swallowing. 



The tadpoles were rapidly increasing in size. Dense 

 crowds of them congregated in the morning at the shallow 

 part of the pond, where the bottom was covered with a 

 thick layer of dead leaves ; they frequently came up to 

 the surface for a moment, as uewts do to breathe. In the 

 afternoon they presented a curious sight : they had left 

 the dead leaves and were spread all round the sides of the 

 pond, grazing on the confervse. 



57. A tadpole was killed and a drawing made of the 

 right hind leg. The toes were distinct ; the first, second, 

 and third were deeply separated from each other ; the two 

 outer ones were less formed. The knee-joint was indicated 

 by an angular bend. 



58. A drawing was made of a tadpole, the natural size, 

 representing the right side. 



58 (2). The right hind leg was then drawn, under the 

 microscope with the two-inch power. It was well formed, 

 showing the thigh, knee, leg, and foot,, the five toes of 

 which were distinct though short and stumpy. 



In the morning the tadpoles were, as usual at that time, 

 congregated amongst the dead leaves ; but in the afternoon 

 they were distributed round the borders of the pond, feeding 

 eagerly on the confervse, a great part of which had disap- 

 peared. 



