DOCTRINE OF THE ACINETA-EOKMS. 101 



seated upon wart-like eminences. The contents were clear, 

 fluid or grmnous, enclosing from one to four contractile 

 spaces. Most of these Acinetae were without peduncles, and 

 had no limitary membrane, although numerous specimens 

 might be seen with a short peduncle and imbedded in a 

 mucoid thick euA'clope; and this was especially observed 

 when the Acinetcs had lived for about a week on the object- 

 glass (figs. 9, 10). Although numerous points of relation 

 exist between these Acineta-forms and Podophrija fixa, Ehr., 

 I am, nevertheless, unable to determine whether they should 

 be regarded as identical, or, Avith Stein, whether Podophrya 

 and Actinophrys should be considered as the extreme links 

 in the morphological cycle of one and the same species."^ 

 The peduncle of an Acineta is a tubular elongation of the 

 enveloping membrane ; whilst, in the membraneless Podo- 

 phi'ya, it is an independent formation. When the Podo- 

 plirya are left in water for a few days iipon the object-glass, 

 they form the very characteristic pedunculate cysts, but 

 under the same conditions I have never been able to follow 

 the Aeineta-forms now in question to the formation of cysts ; 

 the former multiply by division — whilst, in the Acinetxe, I 

 have never noticed the occurrence of that process. What 

 Stein describes as Actinophrys is really a non-pedunculate 

 Acineta ; the Actinophrya have no tentacles, but seta, though 

 perhaps occasionally some of these setee are capitate. In 

 almost every specimen of the Acineta in question, might be 

 seen rotating a round or oval embryo, of various size and 

 position, with one or two contractile spaces (fig. 9). Tliis 

 embryo slowly approached the wall of the Acineta, caused it 

 to protrude a little outwards, and, after remaining for a short 

 time quiescent, it slowly made its way through the wall, and 

 quitted the parent site with the rapidity of lightning, when 

 it had freed about half of itself. This rapidity was so great 

 that the course could not be traced with a magnifying power 

 of 170 diam. (fig. 10). About five minutes elapsed from 

 the commencement of perceptible motion to the complete 

 liberation of the embryo; and on many occasions I saw 

 two rotating embryos liberated in succession. When the 

 embrj^o is half out of the parent-cyst, a transverse ring of 

 very fine vibratile cilia may be perceived at a short distance 

 from its summit. I was prevented from fiu'ther pursuing 

 this observation, which was made in June, and it was not 

 before November that I found the same Acineta, but in far 

 smaller numbers. 



* Steiu, 1. c, p. 143. 



