Ciliaied Pits in Au^i-alian Lo/ti/l PlMnariaaif. 43 



Under a high f»ower the pits are seen to be oval or circular 

 in optical transverse section, with a very characteristic sharp 

 double outline (Figs. 3 and 5), the tiiiek wail of the pit 

 being comp-jsed of almost cubical cells arranged in a circle. 

 These cells in 6^. CfJiruXe/i are slightly granular, and richly 

 ciliated, resembling, in fact, the ordinary epidermic cells dt 

 the ventral surface as described by me in GiOfAfVfM ^^aceri* 

 In Cy, cf^rv.ha the cilia appear, as fiir as can be seen ly 

 focussing at different levels, to l»e continuous right to the 

 bottom of the pit, while the pits themselves appear deep and 

 dilated below. The cilia in the pits woik in a spiral or 

 vortex. The whole ventral sur]^-e of the animal, of c-ourse. 

 also appeared ciliated- Occasionally the wall of the pit is 

 seen to contract suddenly and spasmodically, but tiiis onty 

 happens rarely and with no regularity. 



The observations made upon living specimens of Gk^ 

 CTBTtilfio. were confirmed in the case of Q. oJJja and G. 

 lirieata. In G. alba the pits are very difficult to sce iii 

 spirit-pi-eserved specimens, but they are plainly enough 

 visible in the living anirnaL Fig. 5 shows a ciliated pit of 

 G. alba seen in optical transverse section at the lowest focus. 

 The cells of the wall seem to be less granular than in 

 G. CnxnjJya. and the cilia do not seem to extend quite to the 

 bottom of the pit, which appears to be occupied by a 

 granular substance. The wall of the pit sometimes twitched 

 spa.smodically. In this species the pits are continued right 

 round the anterior margin, and in my preparation the most 

 anterior of them lay right on the e*lge, so that I was able to 

 study them in optical longitudinal section also. Such a 

 section Ls represented in Fig. 4. It wiU l:»e seen that the 

 outer part of the pit is funnel-shaped, that it is narrowest in 

 the middle and dilated at its lower end. The cilia are 

 largest around the external opening, and apparently absent 

 fix)m the dilatation at the bottom of the pit The ceUs 

 lining the lower portion of the pit could not be maile out, it 

 being necesosai-y to focus through a considerable thickness of 

 granular tissue. 



In G. ventroUneata the ciliated pits have the same 

 ap»pearanc-e in optical transverse section as in G^. alba. 



I next \\ished, if passible, to verify the observaticms 

 recor-l*^! above by means of sections^ For this purpose I 

 selected a specimen of G. ventixJ.ineata. in which the pits 



