54 
JANE I. ROBERTSON. 
The account ot* the adult condition has been obtained 
partly from the dissection of one complete and one bisected 
individual (cranial half), whose vessels were injected with a 
gelatine mass at air temperature on a hot tropical afternoon 
(the vessels were first washed out with normal saline solution, 
nitrite of amyl being administered to keep the arterioles 
dilated), and partly from the dissection of a dozen uninjected 
adult heads, which included the cardiac region and heart. 
This account only includes the more obvious details that 
could be ascertained by a conservative dissection of the in- 
jected material mentioned. The account of the development 
of the vascular system has been obtained from the scrutiny 
of serial sections in three planes of a complete series of 
embryos from Stage 23 — when the vessel rudiments first 
appear — to Stage 38, when the adult condition in all but size 
has been attained. The finer morphological and anatomical 
relations of the adult, therefore, have been noted in conjunc- 
tion with the examination of the development of the various 
parts of the vascular system. Stage 38 of the sectional 
material being considered as equivalent to the adult con- 
dition. The portal system, it will be noticed, is reported only 
in the notes on the development of the venous system, as it 
was considered unnecessary to submit the valuable injected 
specimens to the serious disturbance involved by the dissec- 
tion of the vessels of that system. The study of the develop- 
ment of the heart was further facilitated by the dissection 
under the Zeiss binocular dissecting microscope of embryos of 
varying ages. 
Throughout these notes I have called the distal arterial 
segment of the heart the bulbus cordis. I am aware that it 
is still a matter of debate whether this region of the heart 
is more correctly entitled conus (8) or bulbus, but meantime, 
till a final solution of the question is reached, I have preferred 
to employ a nomenclature that brings this account more easily 
into line with the work of Langer ( 16 ) and Greil ( 9 ). 
I have to express my great indebtedness to Professor 
Graham Kerr for free access to all his valuable Lepidosiren 
