Phylogeny of Animals 511 



longitudinal muscles amid a coelomic fluid, in the formation 

 of cerebral and smaller suboesophageal ganglia as well as longi- 

 tudinal nerves, in the origin of simple eyes adjacent to the 

 cerebral ganglia, iu the structure of the primitive kidneys 

 with their excretory tubes, and in the constituent parts of 

 the reproductive system, points of exact morphological con- 

 tact are made between all of the above named three divisions 

 of invertebrates. We cannot share the opinions of those 

 writers therefore who trace the Turbellaria back to a cteno- 

 phoran and so coelenterate ancestry. 



Now all of the organisms hitherto reviewed as belonging 

 to the Rotifera, Turbellaria, and Nemertinea are soft-bodied, 

 and so easily perishable. Therefore, even though they may 

 have swarmed in fresh-water or marine areas of archsean age, 

 no trace would be left of them. So during evolution of the 

 entire protozoan assemblage we would expect no fossil remains 

 till rhizopodan derivatives like the Foraminifera and Radio- 

 laria had elaborated mineral tests; nor of the lower metazoa 

 would we expect remains till simple siliceous — more rarely 

 calcareous — sponges began to deposit spicules in their tissues; 

 nor of the lower Coelenterata would we expect remains till 

 chitinous and calcareous investments or deposits had begun 

 to form as in marine derivatives from fresh- water hydroids, 

 like the graptolites and corals of cambrian deposits; nor of 

 the Rotifera, Turbellaria, and Nemertinea could other than 

 the minute chitinous teeth have a chance of survival in fossil 

 form. 



For millions of years, therefore, organismal activity and 

 evolution may well have proceeded without the possibility 

 or likelihood of even faint indication from the palseontological 

 side. Yet during this period biotic, cognitic, and even cogitic 

 energy may have combined to elaborate organic structures, 

 that became the wide foundations on which an enduring super- 

 structure could be reared. 



But we shall now attempt to trace how the primitive Roti- 

 fera became prolific originators of numerous higher groups 

 than themselves. 



From rotiferan ancestry the Archiannelida and Annelida 

 evidently originated, as Hatschek, Zelinka, and Korschelt 

 amongst others have indicated. Though Dinophilus is a 

 marine coastal genus, it so perfectly unites structural details 

 of both groups that we may well believe it to have been derived 

 from a more primitive fresh-water rotiferan type, in common 

 with primitive microdriloid worms, or it even may have become 

 modified from an ancient marine rotifer. Now an outstanding 



