OF THE PROTOZOA. ACTINOPIIRYmA. 255 



cylindiical, a little indented in the middle, and I'oimded at each end ; and at 

 the extremities, slight oscillations to the right and left could be perceived. A 

 transverse, and frequently curved, nucleus was visible in the fluid contents ; 

 and a lateral contractile space could be clearly distinguished in the upper 

 parts. The vibrations increased in frequency and force until the segment 

 became whoUy detached and escaped. During the process of division both 

 segments were furnished with tentacles ; but when the oscillations of the 

 cylindrical portion commenced, very fine and short cilia might be seen, though 

 with difficulty, vibrating on the free end, — the tentacles at the same time being 

 retracted, and remaining visible only on the posterior segment. I now followed 

 uninterruptedly the movements of the liberated segments. They moved for the 

 most part in curved Hues, in the course of which the motile segment appeared 

 to seek the illuminated side of the drop of water. Cilia could not be perceived 

 over the whole sm-face. The contractile space during the movements was al- 

 ways in front. The motions were rapid, but still such as to allow of their being 

 followed with a magnifying power of 370 diam. After waiting patiently for 

 twenty minutes, I saw the motion cease ; and at the same time short tentacles 

 made their appearance, which were protruded more and more ; and in a few 

 minutes afterwards the segment regained the spherical form : thus, after 

 moving about freely for a time, it was again transformed into a Todoplirya. 



" This process of division was witnessed by other observers. It takes place 

 more especially when sufficient nutriment is supplied by numerous Stylony- 

 cMce to the PodopTiryce. The Podoi^hrya does not always divide into two 

 equal halves ; the segments are more frequently unequal. After repeated 

 division, the specimens always become more transparent." This temporary 

 production of vibratile cilia from the surface of one of the Actinopliryina, in 

 connexion with the process of fission, is a phenomenon so opposed to received 

 notions, that it will necessarily be admitted with great reserve until confirmed 

 by repeated observation. 



The process of Gemmation is recorded by Lachmann to occur in Dendrosoma 

 radians, a being of which we know too httle to pronounce with certainty if it 

 be one of the Actinophryina or of the Acinetina. He says (op. cit. p. 231) — 

 " In Dendrosoma radians, Ehr., a branch of the nucleus grows mto the bud 

 whilst it still remains united to the parent animal." 



Reproduction by Embryos or Germs has been presumed by several autho- 

 rities. Stein, in pursuing the history of the organisms he identified with 

 ActinopJirys Sol and PodopTirya fixa, satisfied himself of the successive 

 development in their interior of a ciliated germ, which he compared to the 

 gemma of a Vorticella, into which, indeed, he supposed it subsequently to 

 ftdly unfold itself (XXIII. 2, 4, 5). However, as before noted, Cienkowsky 

 rejects the beings observed by Stein from Actinophryina, and treats them 

 as Acinetina ; yet he, at the same time, confirms the production of ciHated 

 motile embryos within Acineta, but declares them reconverted into similar 

 Podophryce to those that give birth to them. Apart from the researches of 

 Stein, which have invoked so much attention to the development of Protozoa 

 generally, and particularly to that of Actinophryina and Acinetina, the idea 

 that the members of the former family probably reproduce themselves by 

 germs has been suggested by the occurrence of very minute individuals, 

 either alone or in clusters. Thus KoUiker remarks (op. cit. p. 34) that the 

 smallest individuals of Actinophrys Sol measured only 0-01"' to 0-02'", and 

 presented very inconspicuous and few granules, and that the granular and 

 vesicular corpuscles within the nuclear portion of the body may be germs 

 just beginning to be evolved. Mr. Weston is also led to believe in the 

 internal generation of minute germs ; but the obseiTation he records, as 



