240 W. N. F. WOODLAND 



chamber or passage and ootype when present and the ' antrum 

 feminmum ' serving as vagina, and Dr. Plehn's first idea of 

 regarding Sanguinicola as an aberrant and much modified 

 Turbellarian has still much to be said in its favour, both from 

 the points of view of the genitalia and the gut. Odhner's com- 

 parison of Sanguinicola with certain Malacocotylea was of 

 course based on Dr. Plehn's second but, as I believe, erroneous 

 description of the genitalia of Sanguinicola. 



The testes (tes) are bounded anteriorly by the gut sac, and 

 laterally and posteriorly by the ovaries (PI. 18, figs. 1,2). They 

 consist of large ovoid or spherical capsules connected with the 

 main vas deferens in the median line by transverse ducts. 

 The main vas deferens (vd) is conspicuous in stained prepara- 

 tions by reason of its longitudinally striated muscular walls, 

 and anteriorly it lies ventral to the oviduct. In occasional 

 specimens there appear to be two or three main longitudinal 

 trunks of the vas deferens anteriorly instead of one. Imme- 

 diately posterior to the ovaries the vas deferens lies below the 

 oviduct, but turning to the right (viewed dorsally) it passes 

 above the dilated oviduct, then, becoming considerably 

 dilated, bends sharply to the left (lying parallel with and close 

 behind the dilated limb of the oviduct), and then, as sharply 

 bends again to the right, where it enters the penis which lies 

 posteriad and to the left, and opens to the right of and shghtly 

 behind the opening of the vagina. The directions in which the 

 penis and the vagina lie are approximately at right angles to 

 each other, and if we imagine two Sanguinicola to apply their 

 ventral surfaces together, then the direction of the penis of 

 one Sanguinicola %\ill coincide more or less with the direction of 

 the vagina of the other, one (or both) of these Sanguinicola 

 perhaps holding on to the wall of the blood-vessel by the spiny- 

 edged furrow of the opposite surface. 



During copulation — a process which I assume to result in 

 a mutual exchange of spermatozoa between two Sanguinicola — 

 the spermatozoa must, in each animal, traverse the vagina and 

 reach the fertilization chamber, where fertilization occurs. 

 After fertilization I assume that the eggs are extruded through 

 the vaginal pore into the blood. Since these eggs are devoid 



