STUDIES ON THE ECTOPAEA,STTIC TREMATODES OP JAPAN. Jjg 



PL XIV, figs. 2 & G); while in CalicoUjle and Mlcwcotijlc reticulata flic 

 vitelline lobes are distinctly bnt less completely separated from each 

 other (PL III, fig. 4; PI. XIX, fig. 9). In Tmlomum (PI. XXI, 

 fig. 7) and CalicotyJe (PI. XXI, fig. 9) I have observed a thin bnt 

 distinct membrane snrronndina; the lobes ; bnt in most other o-enera 

 they seemed to be contained in mere cavities of the mesenchyma 

 destitute of any lining membrane. 



The yolk-cells contained in the lobes present different aspects ac- 

 cording to the stages of development. The ripe cells are of 

 very diiferent size-^ in different genera,; but present nearly the same 

 aspect in all. While in the vitellarium, they are of various forms ac- 

 cording to the pressure of the neighbouring cells; but when freed they 

 invariably assume the form of a regular sphere. Each cell is provided 

 with a distinct, refi-active membrane (of tolerable tliickness in Blono- 

 eotijlc Ijimae, PI. XVIII, fig. 5), and contains numerous, yellow, re- 

 fringent granules. The vesicular nucleus usually occupies a central 

 position, genei'ally stains well, and contains a single nucleolus ; it 

 sometimes loses its affinity for stains, but ahvavs subsists to the verv 

 last. The protoplasm seems mostly to have entirely disappeared in 

 the ripe cells; but sometimes it remains as a slightly staining network 

 between the yolk-granules (PI. XX I, fig. 7). Besides the ripe yolk- 

 cells above described, there are, especially in the peripheral part of the 

 vitelline lobes, intensely staining cells of a much smaller size, closely 

 pressed against one another, and Avith a homogeneous or, in the larger 

 ones, a finely granular protoplasm. The nucleus is clear and vesicular, 



1). I append here in the form of a foot-note the results of the measurements of yolk-cells 

 in different species. The figures give the diameter, and are in most cases the average of a 

 number of measurements (not less than five) : A.rine luiterocerca, 0.03 mm. ; Microcotyle caudata, 

 0.035 mm. ; 31. reticulata, 0.015 mm. ; DlcUdophora tetrodonis, 0.022 mm. ; Diclid. .■«>.ss(7(\% 0.028 

 mm.; Onchocotyle spinacis, 0.032 mm.; Mojwcoti/le Ijimnf, O.OlSi mm.; EpiltdeUa orata, 0.021 

 mm.; Tristomtim rotiindum, 0.015 mm.; Tr. foliacemii, 0.019 mm.; Tr. ornic, 0.016 mm.; Ti: 

 sinuatum, 0.018 mm. ; 



