2 MATHILDE M. LANGE 
I wish to thank him for the interest he took in its progress. I 
also wish to express my thanks to Professor Hescheler, in whose 
laboratory I finished this study, and to Dr. Marie Daiber. Their - 
valuable suggestions were of great help to me. 
The specimens necessary for the work were gathered at the 
Zoological Station of Naples and at the Musée Océanographie 
at Monaco. Octopus vulgaris, Eledone moschata, and Sepia 
officinalis were the three species chiefly employed. At first I 
encountered some difficulty in keeping the animals. My experi- 
ence taught me that non-transparent aquaria were better 
suited to the purpose than plain glass basins and that the water 
must flow into the basin slowly, as a strong current is harmful 
to the well-being of the animals. If the basin is large enough, 
it is advisable to turn the water off for a couple of hours every 
day. The food consisted mainly of live crabs. In case the basin 
is inhabited by more than one animal, it is best not simply to 
throw in the food, but to feed each animal singly, in order to 
prevent fighting, as the animals often injure their arms in this 
way, and such injuries are liable to retard regeneration. Ani- 
mals whose lens was extirpated were narcotized in a solution 
which consisted of four parts of 25 per cent alcoholic chloreton, 
and 96 parts water (sea-water). The animal remained in this 
solution from three to five minutes. In order to hasten revival 
after operation, air was pumped into the mantel-cavity and 
pressed out again. This proved quite a stimulant to respiration. 
The narcotic poison which is secreted by the gills generally 
gathers in the funnel. It is advisable to rid the animal of this 
poison by inserting a probe into the funnel. 
The specimens were fixed in the following solutions: Flemming’s 
strong mixture, Hermann’s solution, a mixture of formalin, 
alcohol and acetic acid, and also in a mixture of mercuric chlor- 
ide, alcohol and acetic acid. Several pieces were fixed in 10 per 
cent formalin and several in neutral formalin. If enough ani- 
mals are available, it is advisable to fix an entire animal for each 
successive stage, but if the scarcity of animals necessitates the 
use of one and the same animal to produce several stages, it is 
imperative that regenerated ends be cut off under water. Special — 
