144 GENERAL BIOLOGY. 



Study in a watch-glass with a hand-lens. 



VII. Observe the circulation in the gills of a living 



tadpole. 



Examine in a little water in a watch-glass with 

 microscope , AA 2. 



VIII. The early embryo. Prepared transverse 



section. Study with AA 2 and D 2. 



1. The ectoblast (two-layered). 



2. The neural tube. 



3. The notochord. 



4. The archenteron. 



5. The mesoblast. 



(a) Somatic. 



(b) Splanchnic. 

 Sketch, much enlarged. 



IX. The dissection of the tadpole. 



Dissect under ivater. Pin the tadpole, dorsal side 

 down, through the ba.se of the tail and the roof 

 of the mouth. 



Observe : 



1. The mouth and the horny teeth. 



2. The eyes. Are eyelids present? 



3. The water-pore from the branchial chamber. 



On which side is the pore ? 



4. The anus. 



Open the abdomen by a median incision of the ventral 



body-wall. 

 Note: 



5. The coiled intestine. Uncoil it. 



