ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
155 
rise to the growth in length of the embryo ; and these centres of growth 
occupy the same relative positions in location and in sequence of time, 
and probably to each are due the same parts of the embryo. He believes 
that the best way to regard the area of secondary proliferation is to 
consider it as a single area whose sole function is the addition of cellular 
units to the posterior end of the previously existing embryo. 
Transformation of the Aortic Arches in the Frog.* — M. S. Jourdain 
finds that the statements regarding these arches current in text-books 
are not as correct as are ordinarily supposed. The tadpole, as is well 
known, has four pairs of gills ; they are supplied by blood-vessels, for 
which the author proposes a new terminology. He proposes the term 
bulbar arch for the four large vessels which bring venous blood to the 
gills. The subdivided part of each of these arches he calls the hypo- 
branchial vessels, while the epibranchial vessels are those which carry 
the blood to the arteries. The epibranchials on each side are connected 
with one another by anastomosing branches which he calls the con- 
nective branches. Finally, it is important to note the presence of an 
anastomosing plexus which he calls the interbranchial. This establishes 
a communication between the hypo- and epibranchial vessels. In the 
first arch the vascular network which represents the interbranchial 
establishes a direct communication between the first bulbar arch and 
the carotid-lingual. The interbranchial becomes the carotid gland ; the 
connective between the first and second arch disappears. In the second 
arch a wide canal is formed by means of the interbranchial between the 
second bulbar arch and the origin of the aorta. The connective between 
the second and third arch disappears. The transformation of the third 
and fourth arches is more complex. By the intermediation of the 
third interbranchial and the connective between the third and fourth 
arches, the third bulbar arch becomes continuous with the afferent 
vessels of the lung or pulmonary artery, the chief origin of which is 
the epibranchial of the fourth arch. The fourth bulbar arch, which is 
only a subdivision of the third, becomes useless and atrophies. The 
pulmonary artery of the adult formed by these various branches gives 
rise at the level of the third gill to a vessel which forms the cutaneous 
branch of the pulmonary artery. 
Ova of British iFishes.f — In the fifteenth of his ‘Notes from the 
St. Andrews Marine Laboratory ’ i J rof. W. C. MTntosh has notes on 
the ova and larvae of Gadus virens, and on the ova and larva of the 
Turbot (?), and on an egg resembling that of Arnoglossus megastoma. It 
is found that the Green Cod closely approaches the Cod in its develop- 
ment, but the arrangement of the pigment distinguishes it from a very 
early stage. 
Larval Excretory System of Calamoichthys.J — Herr J. Lebedinsky 
finds in the larvae of Calamoichthys calabaricus Smith two lateral strands 
of lymphoid tissue, arising as coelomic diverticula, and containing the 
excretory system. The funnel-canal of the pronephros is long, with 
2-3 spiral coils ; that of the mesonephros is short and without any 
* Comptes Rendus, cix. (1894) pp. 98-100. 
t Ann. and Mag. Nat. Hist., xv. (1895) pp. 90-7. 
t Archiv f. Mikr. Anat., xliv. (1894) pp. 210-28 (1 pi.). 
