ON THE LIFE-HIStORY OF PEDTOELLINA. 243 



not visible. The dorsal organ and the sucker have both dege- 

 nerated, and are represented merely by the " globules" de- 

 scribed by Barrois in various parts of the larva after its 

 metamorphosis. These "globules" are rounded nucleated 

 cells, which do not stain readily with reagents, their general 

 form being shown in fig. 8, &c. 



It is obvious, from an inspection of the two sections figured, 

 that the stomach has now taken up a position inclined to the 

 surface of attachment, the concavity of the alimentary canal 

 being directed somewhat backwards. 



Remarkable changes, already described in part by Barrois, 

 have by this time occurred.^ 



Fig. 9 shows that the aperture of the vestibule has closed, 

 so that this cavity has no longer any communication with the 

 exterior. The vestibule is partially divided into three por- 

 tions, which do not, however, quite correspond with those 

 described by Barrois. The most ventral portion {v. v. in 

 fig. 9) corresponds to the region near the previous vestibular 

 aperture, and is destined to atrophy completely. The next 

 portion (v. or.) is in connection with the mouth (fig. 8), whilst 

 the most dorsal portion (v. an.) contains the anal cone, and is 

 at this stage and later the largest and most important part of 

 the vestibule. The second or oral division still communicates 

 with the ventral portion, whilst it is almost separated from the 

 dorsal or anal division by the growth of the epistome and of 

 the lateral folds. 



In another section of the series it is seen that the oral and 

 anal divisions of the vestibule still communicate by a small 

 aperture, as in the diagram, fig. 16 (a. v. v.). 



The anal portion of the vestibule is very large, and is grow- 

 ing, at the previously posterior end of the larva, away from 

 the surface of attachment. The cells lining this part of the 

 vestibule are obviously engaged in active growth and multi- 



• The following statements will be more readily understood with the 

 assistance of PI. XXII, fig. 16, representing in a diagrammatic form a 

 median longitudinal section through an individual of the same age as figs. 

 8 and 9. 



