ON THE DEVELOPMENT OF LICHENOPORA VERRUCARIA, 118 
It is impossible to avoid being struck with the very remark- 
able similarity between the stage which has just been described 
in Lichenopora and a phase in the development of Pluma- 
tella, as described by Kraepelin (11; see especially pl. i, 
figs. 65—68). The figures given by that observer might almost 
do duty for Lichenopora, except that the ‘‘suspensor”’ is 
rather longer and the “ follicle” less complicated than in that 
genus. The “suspensor’’ of the fresh-water form is, more- 
over, attached to the body-wall instead of being borne by a 
polypide or by a brown body. 
Kraepelin and Braem (4) have investigated the origin of 
this structure in Plumatella, and they both arrive at the 
conclusion that the structure which supports and contains the 
egg is a polypide-bud. Braem, indeed, dissents from the 
statement of Metschnikoff (13), by whom the structure was 
first described, to the effect that it is an ordinary bud; and 
points out certain differences between it and a bud which is 
destined to grow into a polypide. But the embryophore in 
Phylactolemata would appear to be a two-layered bud, and 
the part which corresponds to my “suspensor” is simply the 
inner or ectodermic layer of that bud. 
Braem further calls attention to the occurrence, in the 
morula stage, of certain nuclei which are smaller than those of 
the segmentation spheres. These may possibly have some 
relation with the smaller nuclei which I have myself noticed 
in Lichenopora during Stage C. 
The earliest changes undergone by the fertilised ovum of 
Plumatella, according to Kraepelin’s account, appear to be 
extremely similar to those which occur in Cyclostomes. In 
Plumatella, as in Lichenopora, a time arrives when the 
embryo is a sharply marked spheroidal mass supported by the 
end of the “‘ suspensor.” 
From this stage the development of the Phylactolemata is 
very different from that of the Cyclostomata. In the former 
group the embryo enlarges, becomes two-layered and acquires a 
central cavity which is completely closed onall sides. Oneor more 
polypide-buds are invaginated from the two-layered body-wall 
VOL. 389, PART 1.—NEW SER. H 
