86 Memoirs of the Indian Museum. [Vol,. V, 



Pelococtes exul (Annandale). 



(Plate vi, fig. i ; plate vii, figs. 3, 3a, 36.) 



1907. Metridium schillerianum var. exul (in part), Annandale, Rec. Ind. Mus. 

 I, p. 48, etc., figs. 1, 2, 3, 4; pi. iii, figs. 3, 4. 



My original description of the ' ' variety exul" of Stoliczka' s Gangetic Anemone 

 applies for the most part to Pelocoetes exul but is vitiated by the fact that I re- 

 garded Phytocoetes gangeticus as the young of the species now to be discussed. In 

 the actual diagnosis, however, on p. 48 of the paper cited the characters distinctive 

 of what I regarded in 1907 as young and adult individuals respectively are clearly 

 differentiated. All that is necessary now, therefore, in the way of actual description, 

 is to give a fuller account of the tentacular system, which can only be investigated 

 satisfactorily in specimens killed in a fully expanded condition ; L for the living animal 

 is too sensitive to permit a very detailed investigation, while specimens killed in the 

 ordinary way do not illustrate the peculiarities of the oral disk to anything like the 

 full extent. 



The tentacles, as is stated in the diagnosis of the genus, are disposed in a single 

 inner circle of twelve and in twelve external pedicellate groups. The twelve primary 

 internal tentacles represent the twelve complete chambers, each arising above either 

 an inter- or an intramesenterial space, which is continued into its lumen. In the 

 case of the intramesenterial tentacles the base of each occupies practically the whole 

 of the inner part of the roof of the chamber, while in that of the intermesenterial 

 tentacles it is situated opposite the central incompletely separated compartment 

 formed by two of the six incomplete mesenteries that project into the chamber from 

 the column-wall. These primary tentacles do not differ in structure or form from 

 the others. 



1 I find by far the most satisfactory method of killing these Gangetic species with degenerate 

 basal disks is to allow them to expand themselves fully in a small vessel of water in which natural 

 conditions are so far as possible reproduced. In the case of P. exul I fill the vessel half full of mud, 

 make a hole some two and a half inches deep in the mud by thrusting in a pencil, and plant the anemone, 

 basal disk downwards, in the hole. I then leave it until after dark with just sufficient water from its 

 own habitat to allow full expansion of the tentacles. In the evening, after they are fully expanded, 

 I sprinkle on the surface of the water a few crystals of menthol. In the morning the animals are found 

 completely paralysed. Without disturbing them, a considerable amount of commercial formalin (about 

 sufficient to make up a solution of 5% formaldehyde) is poured into the vessel. The whole is left 

 standing for an hour and the specimens are then removed and cleaned. If they are wanted for histo- 

 logical purposes they are subsequently treated with corrosive acetic solution precisely as though they 

 were fresh material. In cool weather at any rate, I do not find that they suffer from this process to any 

 material extent so far as general histology is concerned, but if any delicate cytological work is to be 

 performed it is better to kill them in a contracted condition. The specimens of anemones of which 

 photographs are reproduced on pis. vi and vii« were killed and preserved in the way described ; it is 

 apparently applicable rather to species with very thin muscular walls than to ordinary fixed forms, and 

 I have not found it altogether successful in the case of Metridium schillerianum. In that of P. 

 chilkaeus it failed, possibly on account of the use of too much menthol. 



