DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 921 
should have an origin so different in the higher animals. However, the condition of 
that organ in the sturgeon, tunny, and other forms would lend colour to such a view, 
even with the knowledge of the special rudiment in such forms as Salmo, Perca, and 
Platessa. 
Towards the end of February, and later, many of the larval wolf-fishes showed a 
whitish streak in the interior of the intestine. It was uniformly opaque white, and 
apparently consisted of nutrient matter. In section this mass presented a series of 
peculiar crystalline and probably fatty bodies. 
The changes which take place in the structure of the digestive tract in Anarrhichas 
are noteworthy, and consist chiefly of the differentiation of the elements of the mucous 
lining, the increase of the circular and longitudinal muscular fibres, and the greater 
complexity of the folds of the walls, chiefly internally, but also externally. In the stage 
just described (17th January) the stomachal part of the canal has attained little develop- 
ment, and its mucous coat shows only a few frills of finely granular epithelium. As 
development proceeds, however, the cesophageal region of the canal is thrown into a 
complex series of frills, and the mucous lining is supplied with large globular glands. 
In the oldest stage (20th June) the folds of the cesophageal region are more complex 
than in the earlier stages, many of them being subdivided, and the longitudinal fibres 
(inside the circular) are more distinct dorsally and ventrally. The glands are arranged 
as a close and somewhat regular series of globular bodies along the inner surface of the 
folds (Pl. XXVII. fig. 5). Proceeding backward the complexity of the folds increases, 
while the canal becomes rounder, the lamellae being pinnate in transverse section, from 
the number of the secondary folds. The globular glands now cease in the walls of the 
folded ridges, and an alteration occurs in the appearance of the latter, which assume a more 
or less circular condition in section, and in their wide bases are a series of large circular 
areole,* probably glandular (dre, Pl. XXVII. fig. 4), the inner wall of the gut over 
these being composed of closely-set cylindrical epithelial cells. These globular spaces 
also occur under the wall, where there are no lamelle. The calibre of the canal 
becomes smaller and the lamella thicker, a few secondary processes or folds appear- 
ing on their surface. The latter has fine columnar epithelium, and the  sub- 
mucous tissue is composed of granular glands, probably modifications of the large areolee 
in front. These lamellze become more distinctly pinnate before ceasing at the pylorus. 
The wall of the canalis highly muscular, the fibres forming a complexly interwoven layer 
externally. The next region of the canal to be distinguished is that behind the valvular 
folds of the former, and it is characterised by its thinner muscular walls, and the change 
in its glandular lining, for the numerous simple folds around its walls have coarser and 
more lax epithelium than the foregoing. Externally is a peritoneal investment (with 
probably a few muscular fibres), then longitudinal fibres grasped between the outer and 
the next layer, with, finally, an internal circular layer of fibres. 
Posteriorly, the gut diminishes in calibre, and by and by the folds chiefly affect the 
* These areolie in the sketch are perhaps too conspicuously cellular. 
VOL. XXXV. PART III. (NO. 19). fh ae 
