286 Mr. H. J. Carter on the Fresh- and Salt-water 



to precede and prepare the endoplasm for its rotatory function, 

 and thus to be, as in Actinophrys Eichhornii, a normal condition 

 (Annals, ser. 2. vol. xix. p. 13, " Development of Root-cell and 

 Nucleus in Chara"). 



I do not mean to state that the " vacuoles " are " contracting 

 vesicles," because, while they are stationary, the contracting ve- 

 sicle, singly or in plurality, here and there is generally observed 

 among them in full activity. But I am not so sure that they may 

 not be a part of the system of which the contracting vesicle is 

 the active organ. The occasional coalescence of the vacuoles, and 

 their occurrence in the cortical part or ectosarc alone (figs. 4, 5) 

 or when throughout the Actinophrys (as in figs. 6, 7), those of 

 the ectosarc being differentiated by size, &c, from those of the 

 endosarc, lead me to the inference that the spumaceous state of 

 A. Eichhornii is due to a simple aqueous vacuolation, which 

 forms part of the system of which the contracting vesicle, as 

 just stated, is the chief agent, and therefore that its function 

 probably is partly, if not chiefly, that of aeration, wherever it 

 may occur as a normal adjunct. It is worthy of remark, while 

 on this subject, that the young Pythium entophytum, on issuing 

 from the parent capsule as a simple monociliated spherical body, 

 apparently without contracting vesicle, sinks down almost imme- 

 diately, and at the same moment presents the contracting vesicle, 

 which, for a time, by the rapidity of its action and the size to 

 which the inflation extends, seems to threaten destruction to the 

 delicate little Rhizopod, until its function (which certainly looks 

 like one of aeration) has had its full effect, when the contracting 

 vesicle returns to its normal condition, the cilium disappears, 

 and the little Pythium assumes the form, and progresses after 

 the manner, of Actinophrys. 



As regards the presence and absence of the contracting vesicle 

 in the Rhizopoda, but more especially in the family which is 

 now under consideration, I think it of no specific value whatever. 

 It may be present singly or in more or less plurality, or absent 

 altogether, according to circumstances; but in many Rhizopods, 

 when present in its normal state, it seems to have a fixed posi- 

 tion in the animalcule, as in Euglypha, Arcella, &c. 



Again, the presence or absence of the nucleus in Actinophrys 

 appears to be contingent. It is probably present in all the 

 the younger forms ; but as they advance towards the production 

 of the new brood, it may disappear in the formation of germ- 

 cells alone, or it may partly furnish germ-, and partly sperm- 

 cells, in which case the spherical bodies in the endosarc of A. 

 Eichhornii may also, perhaps, originate from the nucleus, as con- 

 jectured by Dr. Wallich (/. c); but if the nucleus furnishes the 

 germ-cells alone, then the others may be developed in the 



