Ciliated Pits in Australian Land IHanarlams. 45 



that they are sense organs, and for my own part 1 am 

 inclined to regard them as olfactory. They probabl}^ occur 

 in all land Planarians, and it is not unlikely that they are 

 homologous with the cephalic pits of Nemertines, as sug- 

 gested by Professor Moseley. 



DESCRIPTION OF PLATE V. 



(Figures 1 to 5 were drawn from living specimens.) 



Fig. ]. — Geo plana ccer idea (blue-tipped variet}^). Anterior 

 extremity crushed flat and examined under 

 Zeiss A, oc. 2, as a transparent object, 



e.— Eye. 



c. p. — Ciliated pit. 



I. I. — Light line in which the ciliated pits 

 lie. 



Fig. 2. — Geoplana coendea (blue-tipped variety). Portion 

 of the above more highly magnified. Lettering 

 as before. The blue specks represent the 

 pigment cells. 



Fig. 3. — Geoplana coendea (blue-tipped variety). Optical 

 transverse section of ciliated pit. surrounded by 

 pigment cells. 



Fig. -i. —Geoplana alba. Optical longitudinal section of a 

 ciliated pit from the extreme anterior margin 

 (Zeiss F, oc. 2). 



ep. — Epidermis. 



d. — Dilatation at the bottom of the pit. 



ci. — Cilia. 



Fig. 5. — Geoplana alba. Optical transverse section of a 

 ciliated pit ; bottom focus. 



Fig. 6. — Geoplana ventrolineata. Enlarged view of the 

 ventral surface of the anterior extremity of a 

 spirit - preserved specimen (Zeiss A, oc. 2) ; 

 showing the light lines and ciliated pits. The 

 eyes are not seen, owing to the o[)acity of the 

 surrounding tissues. 



c. p.— Line of ciliated pits. 



