MONILIGASTER GRANDIS, A. G. B. 330 
dorso-tegumentary vessel close to its origin. Now if it were 
the usual thing for blood to enter the dorsal vessel from the 
dorso-tegumentary vessels, there would, judging from analogy, 
be valves which, acting mechanically, would prevent blood 
taking the reverse direction during the powerful contraction of 
the dorsal vessel ; if, on the other hand, the normal course is 
for the blood to pass out into these dorso-tegumentary vessels, 
the sphincter muscles on the latter would regulate the amount 
so passed out. I do not believe that any great quantity of 
blood flows through these vessels at all, but that what flow 
there is is an outward one, and one which would serve to 
increase the pressure in the peripheral capillaries, and could 
be varied in amount from time to time and regulated.! 
1 Benham thinks that the dorso-tegumentary vessels bring blood to the 
dorsal vessel. He is speaking of Lumbricus, but, as far as I can see, 
there is very little difference between Lumbricus and Moniligaster in 
the matter of the vascular system. The diagram (fig. 34), represents the 
state of things in an ordinary segment of Moniligaster. In this figure I 
have inserted various arrows to indicate the possible direction of the blood- 
flow. Now I think that there is no question as the correctness of these arrows 
>>——, and I believe that these arrows 3>—— are also rightly placed ; 
Benham considers these arrow -+>——> to be correct. I consider the 
question settled in Moniligaster by the valves; Benham thinks that his 
view is confirmed by the arrangement of valves in Lumbricus. Setting 
aside for a moment the question of valves, let us follow out his view. He 
says, that in all these places blood is flowing out from the subneural vessel ; 
very well, where does it flow into the subneural ? The subneural is, as far 
as I can make out, always a part of a system of vessels of which the latero- 
longitudinals form another part; now this system is known to be connected in 
Moniligaster and Lumbricus with the dorsal vessel (or a pair of hearts). 
It is from the dorsal vessel (or hearts), then, that the subneural must get its 
blood, which means that blood must flow, according to Benham’s theory, from 
the dorsal vessel into not only the subneural but into the whole system, 
including the latero-longitudinals ; but branches of these latero-longitudinals 
evidently play an opposite réJe to the branches of the ventro-tegumentary 
vessels in the anterior part of the body, and if the latero-longitudinal vessels 
serve as arteries, the ventro-tegumentary vessels must serve as veins, and 
carry blood into the ventral vessel (in the anterior region of the body). I 
have already given my reasons for believing that this is not the case in Me- 
gascolex (I. c., p. 77), and I think that they hold good, mutatis mutandis, 
