Rhizopoda of England and India. 287 



substance of the ectosarc, as their occurrence there, apparently 

 in all stages of development, seems to imply. 



Lastly, then, it may be asked, What are the specific distinc- 

 tions among- the Actinophryans ? To which it must still be 

 replied, Future observation must determine. 



ACINETINA, Clap. & Lach. 



I have observed several species of Acinetina in both the fresh 

 and salt water of the island of Bombay, viz. Podophrya fixa, Ehr., 

 P. quadripartita, Clap. & Lachm. (on Epistylis), Spharophyra, 

 C. & L., Acineta tuberosa, Ehr., and two or three others unpub- 

 lished, of which I hope to give descriptions and delineations at 

 some future time, my object being now more particularly to 

 direct attention to the two commonest, and therefore those with 

 which I am most conversant, not because they are new (for this 

 they are not), or because they present differences which I think 

 hitherto have not been noticed, but because they serve best to 

 illustrate phenomena which have not been so pointedly exposed as 

 they seem to me to deserve. These Acinetina are, no doubt, both 

 forms of one species, viz. of Podophrya fixa ; but while one (fig. 9) 

 inhabits the fresh water of the pools, the other (fig. 10) is found 

 in the salt water of the main drain of the island ; and the dif- 

 ferences between them are, that the former is a little larger and 

 has a conical capsule, with few costa? (fig. 9 e), while the latter 

 has a globular capsule, with many costre (fig. 10 d). That such 

 differences are constant, my sketches of each, made on several 

 separate occasions, go to establish. 



Having thus introduced these forms to the reader, I will now 

 proceed to describe and illustrate the phenomena to which I 

 have just now and often before alluded, but which, as above 

 stated, I do not think have been so prominently brought to 

 notice as they deserve, viz. the remarkable and almost unique 

 example of an Infusorium being able to put forth and retract 

 both vibratile cilia and capitate tentacula as they may be re- 

 quired, while this is apparently effected as much by extem- 

 porization as the stomachal spaces and digital prolongations of 

 Amoeba. These phenomena are witnessed not only when the 

 Podophrya (figs. 9 & 10) undergoes duplicative division, but 

 also during the changes which the young Podophrya undergoes 

 from the time of its exit from the parent to its matured or ten- 

 taculated condition (fig. 11). 



In the first instance, the Podophrya is seen to pass from its 

 spherical to an elongated form, after which it presents a con- 

 striction in the middle, and the young half, becoming oblong, 

 retracts its tentacula and throws out a wreath of cilia (fig. 9a,b). 



