592 ORDER HETEROTRICHA, 



illustrated in the' third part of his and Claparede's joint work on the Infusoria 

 bearing the date of 1858. It has, however, to be observed that these authorities 

 regarded the four Ehrenbergian species of Stentor, viz. S. polymorphus, S. Muelleri, 

 S. Rceselii, and S. cczruleus, as varieties only of the same species, and consequently 

 associated the results of their investigations of the present type and all illustrations 

 of the same with the title of Stentor polymorphus. These fine hair-like setae do 

 not maintain a permanently extended state, but are thrust out or retracted at the 

 will of the animalcule, and would seem, as indicated by Stein, to possess a tactile 

 function and to correspond most closely in their nature with the fine pseudopodia- 

 like threads emitted from the adherent posterior extremity of many other species 

 in their fixed or sedentary conditions. 



The multiplication of Stentor Rczselii through the means of internally produced 

 germs has been ably demonstrated by Claparede and Lachmann and also ostensibly 

 by Stein. By the first-named authorities, treating of this species as S. polymorphus, 

 it has been shown that spheroidal embryos are developed and become detached 

 from the band-like nucleus or endoplast. These embryos vary in diameter from 

 the i-yooth to the i~45oth part of an English inch, and already possess within 

 the body of their parent, in their earlier stage, the fine cuticular cilia only of 

 the general surface, supplemented by a simple spheroidal contractile vesicle ; later 

 on an anterior and short crescentic line of larger cilia makes its appearance, and 

 this ultimately develops into the extensive adoral wreath of the adult animalcule. 

 Claparede and Lachmann, while not successful in tracing the direct passage of the 

 embryos from their parent's body into the outer water, encountered numbers of 

 them in a free-swimming condition, and from these were able to trace every phase 

 of development into the parent form. Although the derivation of these spheroidal 

 embryos from the band-like endoplast has been first authenticated by the autho- 

 rities just quoted, the internal production of such embryos in connection with 

 Stentor ctzruleus was attested by Eckhard so long since as the year 1846,* and 

 was confirmed a few years later by Oscar Schmidt, both of whom witnessed what 

 escaped the observation of Claparede and Lachmann, viz. the actual birth of 

 embryos from the body of the parent. The majority of the supposed internal 

 embryos of Stentor Roeselii, as figured and described by Stein,t present nothing in 

 common with those just described, but are parasitic Acinetae referable to the genus 

 Sphtzrophrya. Their foreign nature is shown not only by their possession of suctorial 

 tentacles and general conformity with the representatives of the genus named, but 

 from the fact also that the endoplast within the bodies of the Stentors with which 

 they are associated remains intact and retains its normal band-like contour in spite 

 of their presence. Stein, however, records, with accompanying illustrations, his 

 occasional observation of a modification of the endoplast unrecorded by any other 

 observer, and which possibly plays an important part in the reproductive history 

 of this species. In these instances the normal band-like or moniliform contour 

 of the endoplast was entirely obliterated and its place occupied by three oval or 

 irregular-shaped cyst-like structures entirely filled with minute, sharply outlined, 

 spindle-shaped corpuscles whose longest diameter did not exceed the 1-45 6oth part 

 of an English inch. On slight compression these cysts, as represented at PI. XXX. 

 Fig. 31, were expelled through the cuticle of the parent animalcule, and bursting their 

 own walls released the enclosed corpuscular contents mixed with finer molecular 

 matters. By Stein the occurrence of this remarkable transformation of the endoplast 

 is dismissed as representing either a kind of fatty degeneration of that structure 

 or as the result of the intrusion and development within its substance of some 

 parasitic organism. The present author is inclined, however, to regard it as an 

 open question whether this does not represent one phase of an as yet imperfectly 

 understood method of multiplication through the medium of minute microspores, 

 harmonizing with similar phenomena of general occurrence among the more lowly 

 organized Flagellate section of the Infusoria. A circumstance slightly in favour 



* Wiegman's 'Archives.' t ' Infusionsthiere,' Abth. ii. p. 254, pi. viii. figs. 3, 4, and 9. 



