MUSEUM OF COMPARATIVE ZOOLOGY. 33 



method of budding (Loxosoma) ; a relatively poorly developed, incom- 

 pletely retractile lophophore ; a complicated system of sense organs 

 and nerves (Loxosoma); sexual and excretory ducts; a typical larval 

 (trochophorc) form, — these distinguish the Endoprocta. On the other 

 hand, the Ectoprocta are marked by a loss of individuality (existence 

 of coDnocoel, Phylactolajmata), by a highly complicated lophophore pro- 

 vided with means for complete retraction, by absence of a complicated 

 nervous system (small ganglion of Gymnolaemata), by absence (?) of sex- 

 ual and excretory ducts, and by abbreviated larval life (passed within 

 the body of the mother). 



Stronger than this argument is the fact that in the development of 

 the tentacular corona and of the alimentary tract — at first without a 

 coecura — Ectoprocta pass through stages more nearly resembling the 

 adult Endoprocta condition than their own adult condition does. 



These facts seem to me to prove, if morphological principles can be 

 relied upon, that Endoprocta are nearer the ancestral form of Bryozoa 

 than Ectoprocta. 



Admitting that the Endoprocta are more ancestral than the Ecto- 

 procta, I cannot conceive how any one can maintain a close relationship 

 with Phoronis. For the line connecting mouth and anus is in Endo- 

 procta ventral, while the corresponding line in Phoronis is dorsal, as 

 Caldwell ('83, p. 372) has shown, and the kidney is a metanephridium. 

 These facts far outweigh, in my opinion, similarities in tentacular corona, 

 epistome, and bent alimentary tract. 



The absence of a true body cavity, and the existence of a water or 

 excretory system ending in flame cells, point conclusively to an origin of 

 Bryozoa from the lowest worms. For such an excretory system is found 

 elsewhere only in Platyhelminthes, Rotifera, and in a modified form 

 in Xemertines (Burger, '91). On the other hand, the existence in the 

 stalk of epithelial (in addition to meseuchymatous) muscles looks like 

 an advance beyond Eotifera and Platyhelminthes. But it does not fol- 

 low that such muscles existed in the ancestors of Endoprocta ; they 

 may have been produced by causes similar to those by virtue of which 

 they occur in Nematodes. 



Hatschek ('77, p. 528) suggested, and Harmer ('85, p. 11, 35) has 

 since shown, that the ganglion of the Endoprocta is to be regarded as a 

 suboesophageal ganglion. Zelinka's ('91, p. 337) discovery of a suboe- 

 sophageal ganglion in Rotifers is interesting in this connection, as mak- 

 ing more probable the assumption necessary for the preceding view, that 

 the ancestor of Rotifers and Endoprocta possessed such an organ. 



