438 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
nutriment is elaborated into a multitude of small eggs, the number of 
which compensates for their unprotectedness. Unusual abundance of 
food might increase this number, or it might have the result of making 
the individual eggs larger, depositories for surplus oils and other 
hydrocarbons, buoyant like the pelagic ova of many fishes. 
When the female parent becomes more highly developed, intelligent, 
circumspect, and alert, the ability to obtain food is doubtless increased, 
but as a matter of fact the ovary is reduced in size. The ova tend to 
be fewer and larger, and the circumspect parent retains them in the 
oviduct till their deposition is most convenient. When this retention is 
prolonged, as in Reptiles, a natural result is the deposition of albu- 
minous or plasmic secondary deposits, or of secondary membranes, or 
even of a calcareous shell. But the secretory activity thus diverted from 
depositing surplus nutriment in the ovary would tend to diminish the 
fertility of the female and to starve the remaining ovarian ova. 
Furthermore, if viviparous development occur, the embryo diverts all 
the spare nutriment to itself. The result is a diminution of fertility, 
a temporary check to the production of ova, but at the same time an 
increase in the chances of survival. This is most marked in cases of 
mammalian utero-gestation, when the claims of the foetal parasite are 
strong, and when moreover the subsequent period of lactation tends to 
prolong the diversion of surplus nutriment from the ovary. 
“ It may be added, in conclusion, that the membrana putaminis of the 
eggs of birds and reptiles is a reticular, but cuticular, membrane, which 
is to be regarded as the homologue of the keratose cuticular secondary 
oviducal membranes of still lower forms, and that it would tend to take 
up calcareous matters in the same way as similar membranes in other 
parts of the body of a vertebrate.” 
Development of Proteus anguineus.* — Prof. R. Wiedersheim has 
had the opportunity of studying the development of Proteus anguineus. 
He finds that the external gill-orifices are ventral in position, and in 
young larvae, as in Selachians, they are near the buccal cleft. The 
external gills first appear in the form of three papillae set obliquely ; 
later on they bifurcate and divide. The growing limbs have the form of 
buds, and call to mind the development of the paired fins of Teleosteans. 
The bend at the elbow-joint is to be seen in larvae 16 mm. long. The 
position of the limb in relation to the wall of the trunk is such that 
the first finger is exactly ventral in direction, but the second dorsal. A 
short, broad tail is distinctly differentiated in larvae 16 mm. long, and 
the fringe of fin that surrounds it is continued forwards, on the back, 
almost as far as the region of the neck. The organs of the lateral line 
are to be seen in larvae 12 mm. long. The coelom appears at 13 mm. in 
length, and the musculature is differentiated at the same stage. 
The pronephros forms a compact coil of tubules which extends over 
three somites ; it communicates with the coelom by two infundibular 
orifices. The pronephros on either side and the ducts lie freely in wide 
venous blood-spaces which correspond to the system of posterior cardinal 
veins. Karyokinetic figures in the blood-cells indicate that division is 
going on in them. The enteric epithelium is capable of amoeboid move- 
* Arch. f. Mikr. Anat., xxxv. (1890) pp. 121-40 (2 pis.). 
