ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
53 
consequently formed morphologically in the wall of the coelom. No 
branchial muscle in Necturus arises in tissue similar to that composing 
the periaxiale Strange described by Goronowitsch as taking part in the 
formation of the branchial musculature in the bird. The history of the 
various somites is given in detail. 
Accessory Optic Vesicles in Chick Embryo.* — Prof. W. A. Locy 
finds that there exist in the brain walls of the chick and Acanthias (six) 
serial differentiations of epithelium that take the form of accessory 
vesicles, closely connected with the optic vesicles. They are very trans- 
itory — lasting for three hours in the chick — and disappear before the 
true brain vesicles arise, with which they might otherwise become con- 
fused. Their existence supports the hypothesis that the Vertebrate eyes 
are segmental, and that the ancestors of Vertebrates were primitively 
multiple-eyed. Since the optic vesicles in many cases arise before the 
brain vesicles, it seems likely that their primitive relation is not that of 
diverticula. 
Significance of Hypophysis and Infundibular Organ. | — Herr B. 
Haller has conducted a very extensive series of investigations on the 
hypophysis and related organs, the animals chosen including representa- 
tives of all the Vertebrate classes. He concludes that the idea that the 
hypophysis is a rudimentary structure is entirely erroneous; it is a 
glandular structure, at first simple but afterwards greatly increasing in 
complexity, primarily opening into the cavity of the skull, and probably 
secreting a substance which serves to keep the brain-membranes moist. 
Primitively, the hypophysis is sac-like at the time of its origin, and this 
condition persists in Selachians and Amniota ; in Teleosteans, Amphi- 
bians, and Cyclostomes, on the other hand, it arises as a solid outgrowth. 
The investigation does not support von Kupffer’s theory that the external 
opening of the hypophysis represents the primitive mouth of Vertebrates ; 
and so far from accepting the correlated theory that the nasal opening 
of cyclostomes represents this primitive mouth, the author believes that 
the cyclostomes are descended from forms with paired nostrils. 
The infundibular gland is entirely distinct in origin and structure 
from the hypophysis, and primitively opens into the cavity of the brain. 
It occurs in relatively few Vertebrates, and although occasionally attaining 
a high development in terrestrial Vertebrates (e.g. Batrachians), has in 
the general case already disappeared in Amphibians. The processus 
infundibuli , on the other hand, though absent in Selachians and Teleos- 
teans, is well developed in most Vertebrates. It has nothing to do with 
a gland. 
Thyroid, Thymus, and Parathyroid Glands.J — MM. F. Tourneux 
and P. Verdun have studied the development of these structures in the 
human embryo. 
The median thyroid arises from a median bud of the bucco-pharyngeal 
epithelium, which grows out so that its anterior end comes into relation 
with the aortic bulb. 
The lateral thyroids arise from the anterior or ventral walls of the 
* Anat. Anzeig., xiv. (1897) pp. 113-21 (9 figs.). 
f Morph. Jahrb., xxv. (1896) pp. 31-114 (6 pis. and 4 figs.). 
% Journ. Anat. Physiol., xxxiii. (1897) pp. 305-25 (3 pis.). 
