ON WANDERING CELLS IN ECHINODERMS. 105 
Hemal system is a less clumsy term than, e. g., ‘‘ systeme 
lacunaire viscéral”” (Prouho), and does not imply that true 
vessels are present, as do “ blood vascular system,” “ blutgefass 
system,” &c.; moreover, it is merited because the system 
seems to contain a fluid rich in nutrient substances, an important 
property of the blood in other animals. 
The term Dorsal organ, recommended by Dr. P. H. Car- 
penter, will be applied to the organ variously called Heart- 
Herzgeflecht (Ludwig), Chromatogen organ (Hamann), 
Glande ovoide (French authors), &c.: the term is a neutral 
one, not implying any particular function. ‘ Glande ovoide ” 
is unfortunate in not being apt to the form of the organ in all 
Echinoderms. 
In so far as it is the “ central organ of the blood system ” 
(which was Ludwig’s reason for using the term “ Herz” in 
connection with it), it might be still termed as Ludwig sug- 
gested but there is not evidence to show that it is the propul- 
sive organ for the contained fluid more than are the tracts 
proceeding from it. Hemal strands is applied to these 
tracts; it is short and expressive, it does not assume the 
presence of true vessels as does “ Blutgefasse,” and it is more 
inclusive than the term “ Blutlakunen.” 
The different hemal strands are distinguished as circum- 
oral, radial, genital, and gastric. 
In Asterias rubens and other forms the gastric hemal 
strands are enlarged compared to the other strands or tracts: 
they have been called “die frei in der k6rperhohle hineinra- 
gende korperchen ” by Hoffmann, and “ glandes lymphatiques 
de la cavité générale” by Cuénot: neither of these can be said 
to be other than long-winded expressions. The term strand 
or tract is more applicable than vessel; for, as has been already 
pointed out, they do not conform to the vessels of Vertebrates, 
&c., in structure, and also each is not necessarily a single 
tube ; it may consist of a number of anastomosing tubular 
spaces. 
The whole hemal system—with the exception of the gastric 
strands—is contained in canalicular spaces, to whose wall its 
