44 Proceedings of the Royal Society of Victoria. 



were plainly visible after preservation in spi)it (Fig. 6), and, 

 after staining with borax carmine, cut a series of thin trans- 

 verse sections across the anterior exti-emity by tlie ordinary 

 paraffin method. I may state that, in order to ensure 

 success, the sections must be cut as thin as possible. One of 

 these sections is represented in Fig. 7 (the muscles, connec- 

 tive tissue, &c., are omitted in the figure ; the nervous 

 system, eyes, and epidermis only being shown). The light 

 lines, in wliich the pits lie, are plainly recognisable in 

 transverse sections by the comparative clearness and freedom 

 from pigment of the epidermis and the tissues immediately 

 below it. The epidermis also seems to be composed of 

 shorter cells, richly ciliated. The exact position of the lines 

 is shown in the figure (Fig. 7, I. I.). The pits themselves are 

 more difficult to recognise, but the outer part of the pit is 

 sometimes visible (provided the section be thin enough) as a 

 depression in the epidermis, situate near the inner side of the 

 light area (Fig. 7, c. i^) ; while sometimes the deeper part of 

 the pit is also clearly recognisable, though not nearly so 

 plainly as in the living animal. Sometimes, owing either to 

 obliquity in the section oi- in the direction of the pit, the 

 inner portion of the latter is cut ti'ansversely at a little 

 distance below the epidermis. Special nerves run out from 

 the cerebral ganglion to the light line on each side 

 (Fig. 7, n), and these doubtless supply the ciliated pits. 

 The eyes, on the other hand, lie directly on, in fact partly 

 imbedded in, the nerve sheath, and are apparently innervated 

 therefrom (Fig. 7). The nerves, as usual in land planarians, 

 appear as lighter, more transparent bands, surrounded by 

 the more deeply staining tissues. 



So far I have only described the ciliated pits as they 

 appear in species of Geoplana. The only species of 

 Rli.ynchodemus in which I have studied them is R. simulans, 

 and only in spirit-preserved material. They are arranged 

 exactly as in Geoplana around the margin of the horse-shoe- 

 shaped anterior extremit3% below the eyes, and a minute 

 study of carefully prepared transverse sections, combined 

 with microscopical examination of the anterior extremity as 

 a whole, has tailed to reveal any points of difference between 

 the two genera in this respect. 



It is in) possible to be cei'tain as to the function performed 

 by the ciliated pits. Theii- position on the horse-shoe-shaped 

 anterior margin, which, it will be remembered, is uplifted 

 when the animal crawls, and their special inners-ation, indicate 



