THE NEMERTINES OF MILLPORT AND ITS VICINITY. 11 
Enopla generally, he says: ‘‘The course of the circulation, so far as observed, is as 
follows. Posteriorly a gentle contraction from behind forward drives the contained 
fluid along the great central vessel to the front, where it is forced through the 
anastomotic into the lateral vessels and the cephalic arch. Hach lateral trunk swells 
with the wave, and the fluid then proceeds to the posterior end to enter the median, as 
before mentioned. In addition to the stream poured into the lateral trunks, another 
passes into the cephalic arch by the vessel on each side, and the counter-currents must 
meet and commingle, returning again during the diastole of the central vessel.” The 
contraction of the lateral trunks in Nemertes carcinophila is stated to be very vigorous. 
With regard to the Anopla, he states that ‘‘ the current is driven by the contraction 
of the vessels now backward, now forward, so that it is rather a kind of oscillation. . 
The dorsal generally contracts from behind forward, and drives the corpuscular fluid, 
not only to the front, but also through the transverse branches into the lateral trunks. 
The latter propel their contents in both directions.” And with regard to Cephalothria, 
“in the living animal each lateral vessel contracts regularly and swiftly from before 
backwards, sending a wave of fluid towards its posterior end, at which the contraction 
ceases. A reversed movement by-and-by takes place, the contents being propelled 
towards the snout. . . . There appears to be little regularity or rhythm in the 
movement of the fluid in these vessels, both occasionally contracting from before 
backwards at the same time. Generally, however, the contractions are alternate.” 
OupEMaNs (11), who made a careful study of the circulatory system in a number of 
forms, seems to have worked entirely with preserved material, by the method of serial 
sections. 
JouBin (8), says: ‘“ Les vaisseaux . . . . sont animés de contractions et de batte- 
ments, mais il n'y a point de cceur distinct. Le sang progresse vers la téte dans les trones 
latéraux, vers la queue dans le trone médian.” Speaking of Tetrastemma flavidum, he 
says: ‘“ Les vaisseaux sont remplis de sang rouge et font des ondulations colorées, saillantes 
sous la peau.” The same author, in a subsequent work (9), says: ‘“‘ Le sang circule 
grace a la contractilité des vaisseaux, car il n’y a aucun organe central de propulsion ; il 
suit une direction determinée ; vers la téte dans le vaisseau median, vers la région caudale 
dans les vaisseaux latéraux ” (thus agreeing with MacInrosu, and reversing his previous 
statement). ‘‘ Le sens contraire est indiqué par Vogt et Yung pour le Tetrastemma 
flavidum. Quand on observe a l'état vivant certaines espéces transparentes, on voit 
les ondes contractiles progresser lentement sur les vaisseaux a intervalles réguliers.” 
Burcer (2) says, with regard to the Anopla: “ Das Blutgefiisssystem wird von mit 
Muskeln ausgestalteten Stimmen gebildet, welche eine Fliissigkeit, die freie Zellkérper 
enthalt, durch den Kérper pulsiren lassen;” but I cannot find any reference to the 
Enopla. I find nothing concerning the physiology of the circulation in the same author’s 
great monograph (3), nor in his later contribution to Bronn’s series (4); though BeENnHam 
(1) says that, according to BURGER, “the blood, in Metanemertines, flows out of the 
dorsal, through the circular vessels, into the lateral ones, returning to the dorsal vessel 
