ON THE LIPB-HISTOEY OF PEDIOELLINA. 157 



dorsale, ou ils finissent par disparaitre, peu a peu. Sans doute 

 il faut voir, dans les deux soies d^crites par Salensky sur la 

 face dorsale du Loxosoma crassicauda, le reste del'organe 

 des sens anterieur" [i. e. the dorsal organ] " qui, d'apres mes 

 recherches, vient occuper cette place." 



I have already (4) explained my reasons for the belief that 

 the dorsal organ at any rate^ and perhaps the sucker, are im- 

 portant organs, which throw considerable light upon the mor 

 phology of the Polyzoa, so that I cannot accept Barrois' con- 

 clusion that these structures have no particular significance. 



It is obvious thatj however accurate Barrois' conclusions 

 (quoted above) may be, they need further explanation. The 

 similarity between larva and adult in the Entoprocta, even 

 in the position of the buds in Loxosoma^ is so striking that 

 some means of comparing the two stages is necessary. I 

 therefore suggest the following explanation of the relation 

 between larva and adult. 



It does not seem to me that Caldwell's theory of the sur- 

 faces of the Polyzoa receives any support from the metamor- 

 phosis of Pedicellina. The short line between mouth and 

 anus remains unchanged throughout the metamorphosis, and 

 in order to prove that it is not ventral, it still remains neces- 

 sary to show that the dorsal organ of the larva is not a brain, 

 and that the larval surfaces do not correspond with those of a 

 Trochosphere. 



Figs. 17 — 19 (PI. XVII) are diagrams representing a pos- 

 sible explanation of the metamorphosis of the Entoprocta, 

 but although founded on the history of Pedicellina, Loxo- 

 soma is the form which is actually (hypothetically) repre- 

 sented. 



Fig. 17 explains a possible conception of one of the earlier 

 stages in the acquirement of the sessile habit by the free- 

 swimming Polyzoon ancestors. The form is, however, to all 

 intents and purposes, a Loxosoma larva, with brain, sub- 

 oesophageal ganglion (not discovered in Pedicellina until a 

 stage later than fig. 10), and a pair of buds, one of which is 

 shown. I believe there are no authentic instances of the fixa- 



