ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
55 
glomi, probably functional during the interval of the development of 
the true glomeruli of the mesonephros. Maas thus maintains that the 
glomi of the pronephros are wholly secondary structures, not entering 
into the definition of the organs. The mesonephros consists of very 
simple tubules furnished with Malpighian capsules, and acquiring a 
secondary connection with the pronephric duct. 
The important general result is that, as regards its excretory system, 
Myxine is intermediate between Amphioxus and Fishes, its mesonephros 
is simple, and the excretory function is in part discharged by the 
modified pronephros. There is no indication of a transition between 
pronephric and mesonephric tubules, the two showing marked histo- 
logical differences. The observations on the mesonephros lend no 
support to Semon’s theory of the coelomic origin of the cavity of the 
Malpighian capsule. 
Excretory System of Bdellostoma.* — Herr W. Felix has subjected 
Price’s work on this subject to a detailed criticism, dealing especially 
with three of Price’s conclusions : — (1) that the whole excretory system 
of Bdellostoma is pronephric ; (2) that the coelom pouches of the 
embryo in stage A 2 arise by a secondary segmentation of the unseg- 
mented body-cavity ; and (3) that the urinary system develops in a 
caudo-cranial direction. Felix does not think that the facts substantiate 
(1). He does not believe in the existence of the coelom pouch, which 
is nothing more than the gradually diminishing communication between 
urinary tubule and coelom. The development is cranio-caudal, not the 
reverse. 
Development of Californian Hag.f — Dr. Bashford Dean gives some 
account of the development of Bdellostoma Stouti Lockington. It 
spawns in the Bay of Monteret, about a mile from shore, in twelve 
fathoms of water, but the eggs can very rarely be dredged, probably 
because they have been deposited among rock fragments or deep in the 
mud. In some cases, however, a hag is caught with an egg-string 
entrapped in its encasing slime. From observations made upon em- 
bryos reared for a time in aquaria, the author concludes that the eggs 
do not hatch within two months. 
Some of the more striking features in the development are the 
following : — 
The neural tract is laid down, nearly in its entire length, before the 
appearance of somites, and without any indication of neuromeres. The 
tract, as in the lamprey, acquires a lumen by dissociation of cells, pro- 
ceeding antero-posteriorly. 
The brain is distinctly tubular, and differs little in calibre from the 
spinal cord up to the time of the appearance of the paired sense-organs, 
of gill-slits, aud of nearly the adult number of somites. The brain 
portion is about one-fifth of the entire length of the neural tube at a 
stage when nearly the adult number of somites are present. 
The numerous (asymmetrical) foldings of the brain-wall, by which 
the regions come to appear, indicate a primitive condition of the craniote 
brain, i.e. that the latter was originally a tube of many vesicles (eight at 
* Anat. Anzeig., xiii. (1897) pp. 570-99 (11 figs.), 
t Quart. Journ. Micr. Sci., xl. (1897) pp. 269-79 (1 pi.). 
