OYICELLS OF SOME LICHEKOPOR^. 
281 
recent writer, Mr. Th. Marsson*, revives Discocciveci and Defrancia 
for Lichenopora , though his Defrancia contains species which, 
according to what I have said above, cannot be placed with Licheno- 
pora, and his Discocavea is entirely based upon the radii being 
uniserial; but this cannot be looked upon as a generic character, 
and even in specific determination must not be used with too much 
confidence, as there are some species where the rays are in parts 
uniserial, in others biserial. 
In some species there are spines arising from various parts of 
the surface of the zoarium, but these do not appear to furnish 
constant characters ; and, further, I have on one or two occasions 
called attention to the great variation to which the shape of the 
peristome is subject in different parts of the same colony ; on 
the other hand, which side of the peristome is prolonged seems 
to be of considerable diagnostic importance. 
The internal “rays” in the zooecial tubes and cancelli should 
be more studied, and I should consider the denticulation of recent 
Heteropora cervicornis, d’Orb. (Journ. R. Micr. Soc. vol. ii. p. 392, 
pi. sv. figs. 9-11), Lichenopora hullata , MacGf., L. ecliinata , 
MacGr., aud L.pristis , MacGr., as the equivalents of the rays with 
knobs in Dntalophora intricaria, B., Lichenopora radiata, Aud., 
L. reticulata , MacGr., L. Holdsivorthii, B., &c. 
Further, the position of the connecting-pores in the interior 
walls of the zooecia should be examined. 
Having seen how many of the characters used for diagnosis 
are variable, it is quite clear that numerous species made on ac- 
count of a difference in some unimportant character can never be 
recognized again, making a better acquaintance with this genus 
very desirable ; audit seems that a knowledge of the ovicells may 
often assist us in more fully grasping the amount of variation 
caused by the conditions under which the colony grew, and may 
show the amount of variation in different parts of a colony. AV r e 
are as yet unable to say how far the ovicells may be trusted for 
specific determination ; but there is no doubt that they are for this 
purpose of value. Also as some species have been described with- 
out ovicells and some with, in cases where the author has not 
appreciated whether they were present or not, exact studies in both 
conditions are required. In so recent a book as Busk’s ‘ Catalogue 
of the British Museum Polyzoa,’ pt. iii., where 14 species are 
described, the ovicells are never mentioned, nor are they in the 
* Bryozoa cler weissen Schreibkreicle der Insel Riigen, 1887. 
