6 MATHILDE M. LANGE 
up to the present not been made a subject of special study. 
There are several papers on the development of the Cephalopoda 
(Kolliker (44), Grenacher (’74), Bobretzky (77), Ussow (’74, 
’81), Viallton (’88)), but most of them treat only of the earlier 
stages or of the development of some particular organ, and none 
of them enter into a detailed account of the normal growth and 
development of the arm. (Guérin has given a short sketch of 
the histological differentiation of the arm musculature, but 
does not mention the morphological changes which take place 
during the process of normal growth. A thorough and detailed 
report on the development of the arm has not yet been published. 
A. Naef’s monograph on the development of the Cephalopoda 
(now being printed) will surely contain a detailed report on this 
subject. 
The histological structure of the arm is the same at the base 
as at the distal end (with the exception of the tip, where the 
tissue is in an undifferentiated embryonic stage). I therefore 
did not pay great attention to the level of the cut or to the 
amount of the arm I severed from the proximal end. In the course 
of my experiments, however, it became apparent that the regen- 
eration of arms cut off near the base required more time (in some 
cases two to three weeks passed before even the slightest sign. 
of regeneration proper became visible)... As my stay at the 
Zoological station at Naples was limited, I generally amputated 
only about one-third of the arm (rarely half of it), as I wished 
to have quite a number of specimens which were already in an 
advanced stage of regeneration. In cutting off the distal portion, 
care was taken that the section plane was as vertical as possible 
to thé longitudinal axis of the arm. I was often surprised that 
no visible traces of blood could be found on the wound immedi- 
ately after operation. In order to be quite certain on this point, 
I carefully dried the tentacle with a towel before cutting and then 
1 At the tip the tissues of the arm are still in an embryonic stage. Distal 
parts of the tip probably regenerate more quickly because they do not require 
so much time to transform their tissue into an embryonic blastema. The proxi- 
mal parts probably require more time for this process, as their tissues are more 
differentiated. 
