170 A. A. W. HUBRECHT. 
metamerism has finally increased after the gastrula stage 
had been passed and the phenomena of kephalogenesis and 
of notogenesis had begun to show themselves. 
For an eventual comparison of the larval coelomic pouches 
as they were described for Balanoglossus by Bateson (’86) 
with what we know about the ccoelomogenesis in Vertebrates 
the indications at the present moment are only of the very 
slightest, too slight for making any further mention of them 
here. 
The presence of an outer larval layer (of ectodermal deriva- 
tion) in the worm-like transition-form that stood between 
this archaic starting-point and the predecessors of our osteo- 
phorous vertebrates, its absence in that which led up to the 
Cephalochordata, the Cyclostomes, and the Chondrophora was 
discussed on p. 151 of this paper. 
A comparison of these hypothetical and intermediate stages 
between the coelenterate and the vertebrate phyla with the 
conclusions to which Woltereck has come, when he, too (’04), 
has stated that in Annelid development phases occur which 
seem to agree with what I have designated by the terms of 
kephalo- and notogenesis, had better be put off to a later 
publication, this last paragraph being more of a recapitulative 
than of a constructive significance. 
I finally call attention to the fact that the unsatisfactory 
state in which our modern comparative embryology leaves a 
number of important phylogenetic problems—I may here call 
attention to O. Hertwig’s own words on p. 898 of vol. I. 1, 1. 
of his new handbook—may partly find its explanation in the 
circumstance that up to now the comparative embryology of 
Vertebrates has been principally founded on what we knew 
of the chick, supplemented by what Kowalevsky and Hatschek 
taught us about Amphioxus, Balfour about Hlasmobranch 
fishes. Now that we have proposed to accentuate the dis- 
tinction between Chondrophora and Osteophora I may be 
allowed to invite younger embryologists to tackle wherever 
they can the early developmental stages of mammals or 
