THE PHYLA OF ANIMALS l8l 



Phylum Trochelminthes 



Minute aquatic animals related to the worms, con- Rotifers 

 sisting in the main of the Rotatoria or rotifers (page 235), 

 but including also the minute fresh-water animals called 

 Gastrotricha, and equally minute marine Kinorhyncha, 

 both so rarely observed that it is unnecessary to discuss 

 them here. 



Phylum Phoronidea 



Phylum Chatognatha 



Phylum Sipunculoidea 



These are small groups of marine animals, which can- Small and 

 not be satisfactorily referred to any of the other phyla. 

 The sipunculoids, from the nature of their early stages, ful 

 have been classed with the annelids, but they are not 

 segmented. Such groups represent Nature's relatively 

 unsuccessful experiments, which have never developed 

 and spread as have the dominant phyla. They are 

 very interesting to the zoologist but of little conse- 

 quence to the majority of people. 



Phylum Annelida (page 237) 



The annelid or segmented worms, including the e&rth- Annelid 

 worms and leeches. In the older classifications all the 

 worms now separated as Annelida, Platyhelminthes, 

 and Nemathelminthes were grouped together as Verrnes. 

 Pratt, in his Manual of the Common Invertebrate Animals 

 (1916), separates the annelids, but treats all the above 

 groups from Bryozoa to Sipunculoidea as subphyla of 

 Vermes. This has the great advantage of avoiding the 

 recognition of small and relatively unimportant groups 

 as phyla, but the assemblage is an extremely miscel- 

 laneous one. It can be roughly defined as consisting of 



