on the Polyzoa. 151 



furnished with an " articular process " at each end of tlie 

 base. 



It may be added that (according to Busk) the special pore 

 of the Adeonere is formed in " at least three distinct ways." 



Without at present discussing- the precise significance of 

 these characters, it may be remarked that the differences in 

 the pores are of very serious import, so serious indeed that 

 these structures are by no means morphological equivalents 

 throughout the series, and possibly have not the same 

 function. 



The Adeonce are furnished with pores of substantially the 

 same structure and exhibiting the same mode of development ; 

 the differences are only met with amongst the Adeonellce] 

 and there can, I think, be little doubt that they leave us no 

 choice but to dismember this genus should it indeed be 

 retained. 



Coming now to a consideration of the diversities existing 

 amongst the pores in this section of the Adeonidee *, as 

 defined by Busk, we find that two very distinct types occur — 

 (i.) the pores are perforations of the main wall of the zooecium, 

 and open directly into its cavity ; they are single or in com- 

 panies, simple or stellate ; or (ii.) they are openings in the 

 elevated tubular peristome, placed immediately under the 

 secondary orifice, and give access, not to the cavity of the 

 cell but to the interior of the peristome at some distance above 

 the primary orifice. The two structures just described have 

 clearly a totally distinct morphological significance, and 

 possibly have also a different function. 



Of the species referred to Adeonella in the ' Challenger ' 

 Report a large proportion are furnished with peristomial 

 openings, and cannot properly be associated in the same 

 generic group with those which have true pores. 



In a previous paper f I have described the peristomial 

 opening as it occurs in Adeonella fuegeyisis^ Busk, and pointed 

 out the essential difference existing between it and the Micro- 

 porellidan pore, which in my judgment is of the same 

 general nature as that of the Adeonce, Waters has also 

 noted the difference between these structures and correctly 

 appreciated its importance J. He proposes to retain the name 

 Adeonella for such forms only as have a peristomial opening. 



* I follow MacGillivray in adopting this form of the family name in 

 preference to that employed by Busk. 



t " Contributions towards Gen. Hist, of Mar. Pol., XII. Polyzoa from 

 India," Ann. & Mag. Nat. Hist, for May 1884. 



X " On the Use of the Aviculariau Mandible in the Determination of 

 the Cheilostomatous Bryozoa," Journ. K. Micr. Soc. ser, ii. vol. v. (1885). 



