150 Eev. T. Hincks's Critical Notes 



XX.— Critical Notes on the Polyzon. By the Rev. TiiOMAS 

 HiNCKS, B.A., F.R.S. 



I PROPOSE in the present paper to discuss a number of miscel- 

 laneous points, structural and systematic, in the history of the 

 Polyzoa, not according to any definite plan, hut in such order 

 as may he convenient. 



1. Family Adeoneae, Busk. 

 ("Report on the ' Challenger' Polyzoa," pp. 177-189.) 



Under the above name Busk, in his latest work *, has con- 

 stituted a family group, in which are included a number of 

 remarkable forms belonging to the genus Adeona, Lamouroux 

 {Dictyopora of MacGillivray), and a somewhat heterogeneous 

 company, many of whose members were distributed amongst 

 the genera Lepralia and Eschara of the older writers. The 

 group is divided into two sections : — (i.) the true Adeona;, 

 characterized (almost universally) by a fenestrate zoarium and 

 a very curious flexible stem ; and (ii.) forms agreeing gene- 

 rally with the above in zooecial character, but destitute of the 

 fenestrate structure and the stem. The old name Adeona is 

 retained for the first, whilst that of Adeonella is assigned to 

 the second. 



The points which are noted by Busk as characteristic of 

 the whole family are briefly these : — (i.) " the presence of 

 three distinct forms of cell " (zocecia, and ocecial and avicu- 

 larian cells) ; (ii.) the absence of ooecia of the usual type, 

 their function being discharged by specially modified zooecia ; 

 (iii.) the presence of large avicularian cells ; (iv.) a special 

 pore (or a number of such pores) on the front of the cell-wall ; 

 and (v.) a peculiarity in the avicularian mandible, which is 



* I cannot refer to Mr. Busk's work at the present time without express- 

 ing my deep sense of the services which he has rendered to all students of 

 the Polyzoa, and of the loss which they have sustained by his death. 

 Not only has he enriched the literature of the Class with a series of admi- 

 rable works, embodying the results of much able investigation and a wide 

 experience, but it is not too much to say that he has been mainly instru- 

 mental in preparing the ground for the present generation of workers by 

 introducing definite principles and systematic order, and supplying a 

 scheme of classitication, wliich, though to a large extent artificial, has 

 been an invaluable help to the student in the treatment of his material, 

 and has largely facilitated and stimulated research. 



It is a matter of sincere regret to me that the criticisms which I venture 

 to offer on some of his later conclusions have been so long delayed, and 

 that 1 lose in consequence the benefit of the candid consideration which 

 he would have been sure to give them. 



