q 
q 
ON RECENT POLYZOA. 487 
advanced stage the peristome rises considerably round the back and sides 
_of the orifice, but not in front, the result being that a sinus is formed 
here. Ina still more advanced stage the margin of the side wall of the 
_peristome is extended across the upper part of this sinus, forming a 
narrow rim, and converting the open fissure into a circular pore, which 
communicates directly with the interior of the tubular peristome.’— 
Annals, May 1884, p. 360. 
The zocecia of the CRIBRILINIDZ appear to me to afford a good basis 
for a natural group, though the area of the cell varies very much in the 
different species. The zocecial features, however, are very peculiar, and 
the forms that are grouped together in the family are beautiful in the 
extreme. In many—both fossil and recent—the whole front of the cell 
below the orifice is either fissured, or marked by rows of punctures 
without fissures. Both the Cribriline and the Membraniporella are 
widely distributed in the present seas; but only the first of these genera 
are found, so far as is known to me up to date, fossil, and very full par- 
ticulars of the species are given in my Fifth Report on Fossil Polyzoa. 
Much might be said about the zocecia having the mucronate character 
in the lower lip of the orifice of Mucronella (Hincks), only that I have 
referred to several remarkable features in the species found in the 
_Ohallenger dredgings. 
For his own justification in the plan of classification adopted by Mr. 
Hineks in his ‘ British Marine Polyzoa,’ the author says, in his prelimi- 
nary essay’ on the subject: ‘The essential structure of the individual 
cell must certainly be accounted the most important point, both in itself 
and as a clue to relationship. . . . Unless we are content with the old 
(and certainly very simple) method of lumping all erect forms together, 
without any reference whatever to the cell, we have only a choice be- 
tween these two courses: to found genera for the variations of growth, 
as well as for the more important modifications of the cell in each family ; 
or to make the zowcium the basis of the genus, and treat the ordinary 
variations of habit sub-sectionally. I was at one time inclined to the 
former method ;? but further experience of the practical work of classify- 
ing the Polyzoa has brought me to a much greater extent into sympathy 
with Professor Smitt’s views.’ Much, however, remains to be done be- 
fore our groups will be wholly satisfactory, as will be seen when the 
student takes up the study of the different families, genera, and species 
enumerated in the present report. 
There are in the zoccium several structural characters, such as 
communication-pores—avicularia—avicularian chambers, c&c. These 
ought to be specially studied, and seeing what admirable work has been 
done in this direction by Mr. Waters and Mr. Busk, I can only say that, 
with all our knowledge, much remains to be done. 
_ Avery special study has been given to the zocecium of Catenicella 
by Mr. Waters (Quart. Journ. Geo. Soc. vol. xxxix. pp. 423-429) some 
particulars of which are given in the text of the present report, but for 
fuller details, attention is directed to the paper itself, especially so as in 
the same paper Mr. Waters (p. 425) gives some account—all too briefly, 
though—of his views on the function of the avicularia. He also refers 
to the classification of the Membraniporx proposed by Dr. Jules Jullien. 
' Ann. Mag. Nat. Hist. Ser. 5, vol. ii. 1879, p. 160. 
2 Ibid. Dec. 1877, p. 523. 
