on the Polyzoa. 155 



cells scattered over the surface of the zoariura are associated 

 witli a few of the gigantic avicularia, which are disposed 

 around them as if for the purpose of defence. They consti- 

 tute a striking and unique feature, and, perhaps, mark the 

 climax of this sort of specialization amongst the Chilosto- 

 mata. 



The division then of the Adeonid^ which exhibits the 

 zooecial structure characteristic of the genus Adeona I should 

 refer to the family Microporellkla3, in which two subsections 

 may be distinguished : — {a) containing species which are desti- 

 tute of gonoecia, but furnished with an external marsupium 

 (type Microporella) ; {h) containing species which are desti- 

 tute of ooecium, but possess (for the most part) gonoecial and 

 avicularian cells (type Adeona). 



This view is sustained by the high authority of Prof. Smitt. 

 He places his Escharijjora mucronata^ which he ranks along 

 with Eschara lichenoides j Busk {not M. -Edwards), and 

 Eschara distoma, Busk, and Porina suhsulcata^ Smitt, which 

 undoubtedly belong to Adeonella, Busk (restricted), in his 

 family Eschariporidas along with such forms as Micropo- 

 rella ciliata and M. flahellum^ Busk. And in his account of 

 P. suhsidcata he says : " It is necessary very carefully here to 

 distinguish the various forms, because in the neighbourhood 

 of this species we have to place the interesting Adeonce, and 

 then to decide from which simpler form that curious growth 

 is nearest to be derived." [' 1^'loridan Bryozoa,' part 2, p. 29.] 

 It is, perhaps, only fair to add that though he gives a precise 

 account of the avicularian cells, Prof. Smitt's attention does 

 not seem to have been specially directed to the gonoecia ; but 

 the fact remains that after a careful study of the zooecial 

 characters, lie saw no reason for isolating Adeona from the 

 Microporellidee. 



Waters has already* referred the species of Adeona and 

 Adeonella, Busk (part.), which he has recorded from the Aus- 

 tralian Tertiaries, to the genus Microporella^ thus fully recog- 

 nizing the atfinities for wiiich I contend, but, at the same time, 

 rejecting (as I suppose) the genus Adeona. Apart however 

 from mere variations in the habit of growth and adaptive 

 modifications of less essential elements of structure, there may 

 be found, I believe, a sufficient basis for a generic group in 

 the remarkable distinction between the zooecium and the re- 

 productive cells and the entire absence of the ooecium which 

 are characteristic of the Adeonce of Lamouroux and Busk. 



* " Chilostomatous Bryozoa from Muddy Creek, Victoria," Quart, 

 Journ. Geol. Soc. for S-w^. 1883, and " Cliilostomatous Bryozoa from 

 Aldinga and the River Murray Cliffs, South Australia," tbid. August 

 1885. 



