330 Dr. T. Margé on the Classification 
to the Vertebrata than these latter to Amphioxus and the Tuni- 
cata. Nay, it even seems very probable that the resemblance 
founded upon the segmental organs does not owe its existence 
originally to heredity, but that it has originated only in conse- 
quence of adaptation to similar conditions of existence, and 
consequently is to be referred to a so-called homoplasy, which, 
as has already been explained in detail, is not sufficient for 
the demonstration of a true blood-relationship. In my 
opinion, that other hypothesis is much more acceptable, ac- 
cording to which both the Annelida and the Provertebrata 
have originally been produced from worms whose body as yet 
exhibited no segmentation at all, such as we may still see 
among the Turbellaria, Nemertina, Chetognatha, Hntero- 
pneusta, and Nematoda. 
With regard to the Bryozoa and Brachiopoda, my tendency 
is towards the opinion that these animals belong to the great 
stem of the Malacozoa. It appears exceedingly probable that 
they branched off very early from the true Mollusca, as is 
sufficiently proved by a careful comparison of their structure 
and conditions of development, and especially the similarity 
of their larvee (modified trochospheres). ‘This view finds 
further support in the interesting form Rhabdopleura, (a diver- 
gent form of the Phylactolemata), which becomes of the more 
importance because, in its external form and internal struc- 
ture, it is very similar not only to the Brachiopoda, but also 
(according to Ray Lankester’s investigations) to the embryos 
of a Lamellibranchiate, namely Pisedium. All this may 
serve as evidence that the Bryozoa, as also the Brachiopoda, 
have originated with the true Mollusca from one and the same 
main stem, and, indeed, very probably by their having, at a 
very early geological period, gradually adapted themselves to 
a sedentary mode of lite, differimg from that of the remaining 
progressive Malacozoa. 
Upon these facts and considerations we have thought that 
we could best represent the true relationships of the Bryozoa 
and Brachiopoda to each other and to the true Mollusca by 
dividing the main stem of the Malacozoa into two branches or 
subphyla, of which the larger branch embraces the so-called 
Mollusca, ¢. e. all the more or less progressive forms of this 
stem (Lamellibranchiata, Scaphopoda, Placophora, Gastro- 
poda, Pteropoda, and Cephalopoda, as distinct classes), while 
the other branch, namely the subphylum of the Molluscoidea, 
includes the Brachiopoda and Bryozoa, originating by means 
of retrogressive phylogenesis. 
With regard to the groups belonging to the stem of the 
Arthropoda, we must remark that, as is well known, the 
