284 Infusorial Circuit of Generations. 



minutes the whole appearance has dissolved and passed into a 

 " germinal cloud " of molecular " vibrionic " cell-life. 



Besides the above circuits of generations, which probably com- 

 prise both the pulsatory Paramecians proper (Aurelia) and the 

 Vorticello Oxytrichans (through the mediation of the " oyster " or 

 " porte-monnaie-grab "), there occur frequently some analogous 

 forms, such as " Kerona " and " Trachelium," 



The last form of all to appear in infusions, &c,, seems to be the 

 well-known Rotifer, the developments whereof are perhaps related 

 to some of those above detailed. It is, however, most probable, 

 accordmg to the observations of Prof. L. Agassiz,* who saw forms 

 resembling the undulate-fleeced (" Paramecium kolpoda ") grubs 

 hredfrom tlie eggs of Planarise,^ that such are the adult forms {if 

 adult). I have only occasionally met these swelled and pear-shaped 

 dusky bodies, travelling both back and forward with equal facility, 

 and remarkable for the staghorn-like designs of their entrails, 

 thereby evincing something like a membrane in then- organization, 

 but the organ being itself of a sort of glandular structure. They 

 are also said to bisect, like the Oxytricha. Some young ostensibly 

 planarian forms, larger than Paramecium Aurelia, blackish, and 

 shaped like a short broad lancet blade, which I have seen " bisect- 

 ing,'' did so only while encysted, rotating in the manner of mill- 

 stones, and the escaping animals had as yet no trace of the visceral 

 organization, as found in the adult Planariae (and also observably 

 developed in Eotifer). 



We are therefore still in doubt as to the true ultimate genus and 

 species, and therefore have to suspend classification ; the points of 

 interest here submitted being the important physiological pro- 

 cesses and transformations on the one hand, and the fallacy of 

 foregone diagnostic terminology on the other. The description of 

 the genetic phenomena of the so-called Fresh-water Algae in their 

 unbrohen continuity of developments, as experimentally ascertained, 

 I reserve for a future paper. — Sillimans American Journal, 

 August, 1871. 



* 'Ann. Nat. Hist.,' vol. ii., 1850, p. 157. 



t This is no doubt what autliors figure and describe as the " adult Paramecium 

 Aurelia," with its staghorn-shaped intestines and swelled bodies. I am also 

 under the impression tliat it was this form which I had formerly frequently 

 observed in what appeared to be spontaneous coitus. 



