BRANCHIODERMA AND BRANCHIOTREMA 



101 



plate weighted down securely, the whole being completely submerged 

 in an aquarium on December 31st, at a temperature of 19°C. On 

 January 8th the cover was raised and the frog remained motionless 

 in the resting attitude. On being stimulated with a glass rod it failed 

 to react at first, but within a minute it became aroused from its 

 lethargy, raised its head above water, came out of the dish and then 

 swam vigorously away. The next day it was perfectly normal and 

 very active. The cutaneous artery of the frog impinges upon the 

 skin in the region corresponding to that^'where the afferent branchial 



POAMMALIA 



PnOTOZOA 



HtLM/(vrHOP^/J[)A 

 RRANCHIODEHjyiA 

 PlPLOBLfKSTtCA 



_J PiAST(J)OZOA 



Fig. 1 



arteries of Necturus enter the cutaneous gills. The winter sub- 

 mergence of the frog (R. temporaria) , as observed under laboratory 

 conditions, was described by G. Newport in 1851. 



The accompanying chart, which may be called a phylograph, 

 without aiming to be exhaustive, has the temporary advantage of 

 being complete in itself. Incidentally it illustrates the principles- 

 of divergence, parallelism, gradation and convergence. Collective 

 organization is determined by parallel lines of rectilinear descent, 

 and divergence is expressed by the binary cleavages which produce 

 these lines. Plastidozoa break up into Protozoa and Metazoa; 

 Metazoa into Parazoa (sponges) and Enterozoa; Enterozoa into 

 Diploblastica and Triploblastica; the latter into Branchioderma 

 and Branchiotrema; these into Helminthopsida and Ichthyopsida; 

 and these again into Acrania and Craniota. Acrania include both 



