82 Mr. A. W. Waters on Australian Bryozoa. 



students interested in geographical distribution, a point witli 

 which I again deal fully. 



Another point to which I was obliged to devote special 

 attention was the indications given by palaeontology as to the 

 relative value of various characters, and this again could not 

 be done by questioning fossils alone ; but recent forms were 

 also examined. This has naturally made me a warm sup- 

 porter of those who saw that the mode of growth and zoarial 

 characters generally must, in importance, be placed after the 

 zooecial. Of the zooecial characters the shape of the oral 

 aperture is the most useful, and this, I have pointed out *, can 

 best be studied by means of the opercula ; and both Busk and 

 MacGillivray, and myself have shown that the avicularian 

 mandibles furnish characters of the greatest value specifically. 

 My own collection of these chitinous elements represents 

 many hundred species, and their importance can scarcely be 

 overrated, for in many cases there are minute characters 

 which are distinctly of specific value, but unless the opercula 

 or mandibles are carefully separated out some of the most 

 important points will not be noticed. It was quite incom- 

 prehensible how Mr. Busk had overlooked so many details 

 in his ' Challenger ' work, until I saw some collections illus- 

 trating these chitinous elements, which he presented to the 

 British Museum, and then it became quite clear that mounting 

 them in mass, surrounded by the integumentary tissues, 

 accounted for his not having seen many things of importance. 

 It is of course very tedious teasing out tliese covers under 

 the microscope ; but for fresh descriptions or doubtful cases 

 it should, if possible, be done ; also calcined preparations of 

 a portion of the zoarium should be made to show the calca- 

 reous structure, and decalcified pieces should also be mounted. 

 This can best be done in glycerine jelly, the air being 

 removed after decalcification by prolonged soaking in spirit, 

 and then the specimen must be transferred to a mixture of 

 glycerine and spirit, and thus gradually into pure glycerine. 

 Buch genera as Catenicella should be thus studied. 



There are only five species of Catenicella in these collec- 

 tions, and they have been a good deal knocked about by the 

 waves. The opercula of this genus have so far not received 

 any attention, nor in this family are they likely to be of 

 so much use as in many others, since there are many species 

 with scarcely distinguishable covers. There appear, how- 



* " Tlie Use of the Opercula in tlie Detei'mination of the Chilosto- 

 matous Bi^ozoa," Proc. Manchester Lit. & Phil. Soc. voL xviii. p. 8 ; "On 

 the Use of the Avicularian Mandible," &c., Journ. Microscopical Soc. 

 ser. 2, vol. v. p. 774. 



