On (in Australian Land Nemevtine. 109 



proceed to describe the condition of the parts concerned in 

 Geouemertes austral iensis. 



In the first place the hiteral organ of each side lies almost 

 entirely below the brain, as will readily be seen by reference 

 to Fio-ure 4. 



On the ventral surface of the head there is a sHght 

 transverse groove (Figs. 5, 6, 12, (jr.) in wliich He, one on 

 either side of the mid-ventral line, the openings of two 

 narrow and deep pits — the ciliated ducts* or cephalic pits. 

 Following one of the ducts (Fig. 4, c. jx) inwards from the 

 external opening we find that it passes obliquel^y upwards 

 and backwards and, at the same time, towards the side of 

 the body, so that in Figure o it appears cut transversely. 

 When it reaches the level of the anterior surface of the 

 brain the duct runs into the substance of a dense mass of 

 small-celled tissae (Fig. 4, I. g.) This is evidently the 

 epiblastic portion of what Hubrecht calls the posterior 

 brain-lobe, but here no longer posterior and also widely 

 separated from the rest of the brain. Fi-om its position and 

 relations I propose to call this part the '-ganglion of the 

 lateral organ." 



The ganglion of the lateral organ is an elongated mass of 

 densely packed, small cells, lying longitudinally beneath the 

 anterior and dorsal lobe of the brain. It is somewhat bent 

 U})on itself and narrows posteriorly. Near its hinder end it 

 receives the nerve from the brain already mentioned, which 

 joins it on its dorsal aspect just as it passes through the mus- 

 cular diaphragm. At its posterior extremity the ganglion 

 of the lateral organ becomes continuous with the curious 

 body marked x. in Figs. 3, 4, 5, 7. This body I take to be 

 the oesophageal portion of the lateral organ mentioned by 

 Hubrecht, and as it is clearly distinguishable from the 

 remainder of the lateral organ, I propo.se to call it the " oeso- 

 phageal organ." The oesophageal organ is very different in 

 histological structure from the ganglion of the lateral organ. 

 It is composed of much larger, nucleated, granular, very 

 darkly staining cells, closely packed together into a dense 

 mass which luns beneath and behind the ventral lobe of the 

 brain (Fig. 4j. Its appearance suggests that it may possibly 

 be glandular, but foi- the present 1 fear it must be regarded 

 as an organ of unknown function. Figure 4 shows that it 



* I have not been able to detect the cilia iu my sections except just by the 

 external opening. 



