— 22 — 



i' body radially symmetrical, composed of five hal. 

 somites arranged in a circle Schinodermataf 



V body quadrilaterally symmetrical, both halves of 

 each somite being present Arthropoda. 



with gill clefts and a branchial skeleton ; or if gill 

 clefts are absent, with a solid anterior process from 

 the alimentary canal serving as a supporting structure 

 h' nerve cord ventral, or both ventral and dorsal nerve 

 cords present. 



i' mouth at the posterior end, near the anus ; with 

 1-6 pairs of tentaculiferous arms forming a lopho- 



phore ; nerve cord ventral Pterobranchia. 



no perforating gill clefts, but a deep groove leading to the mouth 

 on either side ■ a single pair of tentaculiferous arms ; forming 

 by budding large arborescent tubiculous colonies within which 



the individuals are all connected Rhabdopleura. 



a single pair of perforating gill clefts ; 4-6 pairs of tentaculiferous 

 arms ; social, living in large colonies enclosed in a system of 

 ramifiying and sometimes anastomozing tubes, the numerous 

 individuals separate, but probably all produced by asexual budding 

 from the original one Cephalodiscus. 



V mouth anterior, at the base of the proboscis ; anus 

 terminal ; vermiform, without appendages ; both 

 ventral and dorsal nerve cords present ; solitary, 

 and not reproducing by budding Balanoglossida. 



nerve cord dorsal 



i' no definite head ; no limbs, skull, jaws, differen- 

 tiated brain, sympathetic iiervous system, eye, ear, 

 definite heart, spleen or genital ducts ; gill clefts 

 numerous 



during development the mouth moves posteriorly to a position near 

 the anus and the animal becomes sac-like, fixed or inactive ; body 

 enclosed in an organic exoskeleton ; many by asexual budding 



form extensive fixed or floating colonies Tunicata. 



mouth anterior, anus posterior ; body always markedly asymmetrical ; 

 no exoskeleton ; always solitary, and budding.. . . Cephalochorda. 



V with a definite head ; with limbs, skull, jaws, brain, 

 etc. : Rill clefts few Vertebra ta. 



In the following table the various animal phyla are 

 arranged in accordance with the principles outlined in the 

 preceding pages. The several plant groups (included as given 

 in Porter's translation of Strasburger, Schenk, Noll and 

 Schimper's text book of botany) are added to show the paral- 

 lelism between plants and animals. 



Professor Walter K. F'isher suggested the advisability of 

 dividing the Polyzoa into two phyla, which are here called 

 Calyssozoa and Polyzoa. 



