BY G. I. PLAYFAIR. 7 



Reproduction.— The polymorphic character of the various 

 accepted species of Trachelomonas is best shown in the reproduc- 

 tion. It is true, no doubt, that, in permanent waters, propa- 

 gation takes place largely by self-division, ))ut it has been shown 

 above (and indeed it is a commonplace of my experience) that 

 the home of Trachelomonas, and of the green-flagellates generally, 

 is in shallow rainwater-pools which become entirely dry at longer 

 or shorter intervals. Under these circumstances, the Infusoria, 

 flagellate and ciliate alike, reproduce themselves by micro- 

 zoospores formed by the splitting up of the whole body. These 

 micro-zoospores, settling down, form resting-cells, and when their 

 habitat is revivified by rain, the type is reproduced from the 

 resting-cell after a longer or shorter period of vegetative growth. 

 The vegetative stages of Euglend and Phacus are well-known. 

 If the various forms of Trachelomonas were specifically distinct, 

 there would be a distinct resting-cell and course of development 

 for each. But tliough I have paid special attention to localities 

 such as I have mentioned, I have never found any other resting- 

 cell than that which is directly associated with the very smallest 

 sizes of Tr. volvocina. Compare my remarks on the Peridinie?e, 

 "Plankton of the Sydney Water-Supply," p. 541. I have not 

 seen the micro-zoospores, but the act of emission is figured by 

 Stein, I.e., T. xxii , f.lO and 31. The pale colour of the lorica, in 

 forms found in newly-filled rainwater pools or swamps, forbids 

 the idea that the organisms have survived the dry season; they 

 are quite evidently a new growth. 



Lorica. — With regard to the composition of the lorica, Stokes, 

 I.e., p.88, quotes some remarks by Fisher (Proc. Amer. Soc. 

 Micros., 1880) as follow^s : — " On testing with solution of potash 

 or soda .... the spines are detaclied from their bases, whilst 

 the lorica remains unaflfected, either in form or rigidity. Thus 

 the probability is established that these spines, again like those 

 of the Echinodermata, are articulated to the lorica by an organ- 

 ised membrane which yields to the action of the salt, and the 

 separation is eff'ected. On testing with hydrochloric acid, brisk 

 effervescence immediately takes place; the main body of the 



lorica is dissolved The chief constituent of the lorica is, 



therefore, shown to be calcareous." 



