1894.] Zoology. 813 
least, possible that there was a region in which the Galaxiids and 
Haplochitonids were developed, and subsequently representatives of 
those families might have found their way into the regions where they 
now abound." 
In the discussion of the possibilities of the origin of the present 
types of the fresh-water fishes of New Zealand, it appears that Dr. Gill 
is of the opinion that “community in type must be the expression of 
community of origin, and the presence of fishes of long-established fresh- 
water types must imply continuity or at least contiguity of the landsin 
the midst of which they occur at some time or other.” He then adds: 
“ We may be permitted to postulate (fishes being congeneric in New 
Zealand, Australia and South America), that there existed some ter- 
restrial passageway between the several regions at a time as late as the 
close of the Mesozoic period. The evidence of such a connection 
afforded by congeneric fishes is fortified by analogous representatives 
among insects, mollusks, and even amphibians. The separation of the 
several areas must, however, have occurred little later than the early 
Tertiary, inasmuch as the salt-water fishes of corresponding isotherms 
found along the coasts of the now widely separated lands are to such 
a large extent specifically different. In general, change seems to take 
place more rapidly among marine animals than fresh-water represen- 
tatives of the same class.” (Fifth Mém., Vol. VI, Natl. Acad. Sciences.) 
The Carotid, Thymus, and Thyroid Glands form the sub- 
ject of a rather lengthy paper by A. Prenant.’ He had a good series of 
embryos, and studied carefully the histological changes during de- 
velopment. According to him the carotid gland originates from the 
third entodermal branchial pouch, and at first becomes closely con- 
nected with the primitive carotid artery, but later loses this connection 
and becomes united with the head of the thymus. In regard to the 
lymphoid transformation of the thymus, he says that in embryos, from 
25 and 85 mm. in length, there appear small nuclear elements among 
the primitive epithelial cells, which stain deeply and are comparable 
to lymphocytes. The thymus in embryos of 85 mm. and upwards be- 
gins to differentiate itself into an outer cortical portion and an inner 
medulary portion. "The latter is clearer, looser in texture and poorer 
in lympathie elements than the cortical portions. This further be- 
comes differentiated into a peripheral and an inner portion. The 
former stains less, is richer in karyokinetic figures than the latter. It 
"Contribution à l’etude de développement organique et histologique des Thy- 
mus de la glande thyroid, et de la glande carotidienne. A. Prenant, La Cellule, X. 
