
1897.] Embryology. 1025 
favored the homology in his paper on the teleostean lateral line, after 
studying the Selachians he gave it up. Now that the early develop- 
ment of the lateral line is approximately known in Teleosts and 
Selachians, there seems less than ever to be said for the homology. If 
it could be shown that the segmental sense-organs of Annelids, leeches, 
etc., arise from an anterior anlage, which grows and, so to speak, dis- 
tributes the sense-organs along the trunk, the homology might well be 
supported. But as far as I know the invertebrate segmental organs. 
arise 7” situ.” 
‘ The fact that there is in the bass a common alae for the ear, 
branchial sense-organ, and lateral line has certainly no phylogenetic 
significance. It can only be regarded as a convenient method of 
forming these sense-organs which the embryos of certain animals have 
adopted. It, however, serves to emphasize in a striking way the serial 
homology between the organs which previous work has already made 
so probable.” The interpretation of .this latter quotation is somewhat 
obscure and the author’s meaning difficult to read betweeen the lines.. 
If he means that the ear, branchial sense-organs, and lateral line have 
arisen in the adult in the same position found in the adult to-day, and 
have subsequently concentrated in the embryo into a single anlage, he 
brings no evidente forward to support his position. If he means that 
in the adult these three sets of organs arose from a single anterior 
organ, and the ontogenetic phases repeat the ancestral process, then 
the theory seems in better accord with the facts, but his words seem 
to bear out no such interpretation. At any rate, to announce that in 
their origin, which he has himself discovered, there is no ‘‘ phylo- 
genetic significance’’ seems an extremely hazardous affirmation. In 
any case, however, the discovery itself is extremely important, and may 
have an important bearing upon the question of metamerization of the 
vertebrate as contrasted with that of the Annelid. 
The last section deals with ‘‘General Morphological Questions,’’ 
touching mainly upon concrescence and the interpretation of the 
process of gastrulation in the Teleost. <‘‘In the growth of the blasto- 
derm around the yolk, the head end of the embryo does not remain a 
fixed point, as His supposed. On the contrary, the tail end of the 
embryo (posterior pole of the blastoderm) remains a comparatively 
fixed point, as Oellacher first showed, while the anterior pole of the 
blastoderm travels rapidly around the yolk. The point where the 
blastopore closes is thus but a short distance from the original position 
occupied by the posterior pole of the blastoderm. Owing to the 
constant position of the single oil globule, these facts can easily be 



