of the Fishenj Board for Scotland, 
S47 
proximity to the sides of the brain, are widely separated (Plate XV. fig. 17), 
and the infundibuliim and pituitary body are lifted above the oral roof, 
and are suspended in a mass of loose cellular tissue. Below the medulla 
oblongata (Plate XV. fig. 19) similar tissue abundantly occurs, and is bathed, 
no doubt, in colourless lymphatic fluid ; and the disposition of the organs 
al)ove would appear to be due to the enlargement of the lymphatic spaces 
below, for the floor of the medulla oblongata is raised up so as to open out 
its lumen and obliterate the cavity of the fourth ventricle save for a slight 
median depression (Plate XV. flg. 19). The flattened state of the medulla 
and of the hind portions of the brain is thus wholly different from that 
of the herring, the brain of which is remarkably depressed, for in the 
former it is due to upheaval from below, extending as far as the third 
ventricle, and opening out the aquedudus Sijlvii by the elevation of the 
crura cerebri. In later stages a median septum divides this sub-encephalic 
chamber, while from the roof of the mouth two lobose sacs hang down 
and are filled with lymph (Plate XV. fig. 18, ss). A special interest attaches 
to the renal structures in Lophius on account of Hyrtl's determination 
that the adult organ is a head-kidney only. The pronephros, however, 
presents the usual features, and there is a paired Malpighian capsule with 
glomeruli, a complicated series of lateral tubules, and a simple elongated 
archinephric duct, as in other forms. The great development of lymphatic 
tissue in the pronephric region is interesting in connection with Balfour's 
view, based to some extent on a study of the kidney of Lophius^ that the 
pronephros is really a degenerate lymphatic gland. As the archinephric 
ducts descend to the large urinary vesicle, they pass through a posterior 
mass of lymphatic tissue (Plate XV. fig. 15). The figure referred to shows 
the rudimentary generative glands as sac-like protrusions from the mesen- 
tery, solidly built up of rounded cells, and covered by a delicate peritoneal 
envelope. 
Of the development of the paired fins little need be said. They arise, 
as usual, in the form of pads, an ectodermic fold with an intrusion of 
mesoblast ; but the pelvic fins assume a remarkable rod-like form by the 
fifth day, while the base becomes greatly enlarged and develops a basal 
plate of cartilage (Plate XV. fig. 13, cart.) about the ninth day. On the 
fifteenth day they are longer than the whip-like anterior dorsal spines, and 
are so thickened basally as to form etout projections, with a slight bifurca- 
tion, the rudiment of a second free ray. The basal cartilages almost meet 
in the middle line as a cartilaginous girdle (Plate XIV. fig. 7). The head by 
this time is greatly expanded, and, viewed from above, resembles in many 
respects the post-larval example obtained by Professor MTntosh. The 
changes between the advanced embryo (Plate XIV. figs. 6-8) and the 
Interesting form mentioned are apparently so inconsiderable that the 
question arises whether or not the British LopMus really passes through 
the surprisingly grotesque stages figured by Agassiz (1, PI. XVIII. figs. 
2, 3) before reaching the flattened post-larval condition, a question which 
only the capture of eady post- larval stages can decide. 
LIST OF PAPERS REFERRED TO. 
1. Agassiz, Alexander, 'On the Young Stages of Osseous Fishes,' Proc. Amer. 
Acad. Sci., vol. xvii., 1882. 
2. Agassiz and Whitman, 'The Dev. of Osseous Fishes,' Studies from Newport 
Lab., vol, xiv., 1885. 
3. M'Intosh and Prince, ' Dev. and Life- Histories of Teleostean, Food- and other 
* Fishes,' Tram. Roy, Soc. Edin., vol. xxxv. pt. iii., 1890. 
