OUE KNOWLEDGE OF NEW ZEALAND HOLOTHURIANS 121 



about twenty individuals, whereas in the latter position they are usually 

 isolated. The size o£ the open ciliated funnels from the mesentery is usually 

 about 0*147 mm. in length, and 0*054 mm. in transverse diameter across the 

 widest part. 



The form of a ciliated funnel from the mesentery is shown in fig. 25. 

 The entire organ may be regarded as a flat plate with the two sides curved 

 inwards until they meet at the base, but left gaping for the greater part 

 of their length. These ciliated funnels from the mesentery are always 

 situated on the end of a long stalk and all of them appear to be widely open. 

 The centre of the funnel is always filled with a large number of cells which 

 may possibly be coelomic cells carried into it by the action of the cilia 

 occurring on the inside of the funnel (fig. 27). 



The wall of the funnel appears to consist of a single layer of regularly 

 arrano-ed columnar cells bearing cilia on tlieir inner ends. Semon describes 

 the ciliated funnel of Synapta as possessing two layers of cells, an outer laver 

 of peritoneal epithelium and an inner layer of columnar cells. We have not 

 yet had an opportunity of examining these organs in Synajyta, but in our 

 Rliahdomolgus we have not been able to detect the external peritoneal 

 covering. 



The " funnels " which occur on the longitudinal muscle-bands appear to 

 differ from those occurring on the mesentery. They are apparently not 

 ciliated and present vai'ious stages from a mere closed sac-shaped body, at 

 the end of a stalk, to the funnel-shaped body shown in fig. 2&. In the earlier 

 stages of their development these organs appear to be quite solid, and ovoid 

 in form, consisting of a central mass of protoplasm containing a few scattered 

 nuclei, surrounded by a more or less definite outer layer of cells as shown in 

 fig. 28. The central mass of protoplasm later on appears to break up into 

 large cells with conspicuous nuclei, which may be seen in figs. 2Q & 29. 

 At the same time the whole structure increases in size, becomes funnel- 

 shaped, and finally opens at the distal extremity, apparently to allow the large 

 granular cells of the interior (?ova) to escape (fig. 26). 



From a consideration of the above facts, it seems possible that these 

 remarkable funnel-like structures may be parasites. All those occurring on 

 the longitudinal muscles appear to be of the same kind and possibly 

 represent one stage in the life-history of the individual. The cells which 

 escape from these funnels are certainly very different from any other cells 

 occurring in the Holothurian both in size and structure. They may possibly 

 give rise to the " ciliated funnels " of the mesentery or to others of their 

 own kind. 



The open ciliated funnels of the mesentery may thus represent another 

 stage in the life-history, or may even be males, while those on the longitudinal 

 muscles are females. A strong argument in favour of the view that these 

 structures are parasites is the fact that they are much less numerous in some 



