DURING HIS SOJOURN IN THE WESTERN PACIFIC. 537 



through this uniform mass are a number of deeply stained structures shaped like pins 

 with rather big heads (0, Fig. A in text). The pin is embedded in the mass, the 

 head deepest and the point coming to the free surface on which it apparently opens. 

 Sections of these structures are shown in Fig. 7, Plate LIV., the largest was unfortu- 

 nately fractured in cutting. I can offer no suggestion as to the nature or meaning of 

 these organs. 



An occasional egg is seen in the vagina, the lumen of which is bounded by a 

 frayed deeply staining wall recalling that of the penis, and as in that case it may 

 be that this appearance is due to cilia. The vagina is surrounded by a number of 

 unicellular glands massed together into follicles, which closely resemble in structure and 

 appearance the glands surrounding the penis in the male. 



Professor Braun in the article on Trematodes in Bronn's " Thierreich " says that 

 a Laurer's canal is usually absent in the family Monostomidae and is absent in the 

 genus Monostomum. I have not succeeded in seeing one in my sections but Walker 

 has found the canal in all three species he worked at, and in some of my sections the 

 inner end of the uterus and the shell-gland complex was full of eggs and spermatozoa 

 mixed ; it seems more in accordance with what is known of the group that these 

 should have entered by a Laurer's canal than have made their way up the complicated 

 female passages. No spermatozoa were seen in any other part of the female apparatus 

 in my specimens. 



The eggs undergo considerable changes between the time they leave the shell- 

 gland complex and when they leave the body. The youngest egg in the uterus is an 

 oval body containing four or live yolk granules quite discrete and distinct, and 

 arranged in a row (Fig. 6, Plate LIV.). These all stained deeply, and one of them 

 may have been the nucleus which otherwise was indistinguishable. The protoplasm 

 stained hardly at all in this .stage. The egg is presumably fertilized before the 

 shell was deposited. This shell is at first a thin cuticular covering apparently 

 permeable by staining fluids; as the eggs pass down the uterus the shell thickens, 

 and it soon appeai-s with a very distinct double contour. The staining fluid no longer 

 penetrated the thick shell readily and only in those sections stained on the slide did 

 the protoplasm take up any pigment. When this was done however the egg took up 

 the colouring matter uniformly and the yolk granules no longer appeared as separate 

 deeply stained bodies (Fig. 7, Plate LIV.). 



At first the eggs are oval, but about half-way along the uterus a stalk begins 

 to appear. These seem to increase in length — I do not know how — until they are 

 some four or five times the length of the egg. They are not quite stiff but can be 

 bent and sometimes are curved by being pressed against the edge of the uterus, 

 usually however they are quite straight and lie together in parallel bundles recalling 

 the lances in Velasquez's "Surrender of Breda." I never saw an egg with two filaments 

 arising from opposite poles, as Walter figures them, and I never saw the filaments 

 pointed, they always ended squarely, but he mentions that the form of these stalks 

 is very variable and my observations serve to confirm the truth of his last sentence 

 "Demnach niussen wir annehmen, dass die Ausbildung der Eifilainente bei dieser Species 

 variirt." 



