782 MICROSCOPIC FORMS OF ANIMAL LIFE 



up without loss of life. When this circumstance is taken into 

 account, in conjunction with the extraordinary rapidity of multipli- 

 cation of these animalcules, there seems no difficulty in accounting 

 for the universality of their diffusion. It may be stated as a general 

 fact that wherever decaying organic matter exists in a liquid state, 

 and is exposed to air and warmth, it speedily becomes peopled with 

 some or other of these minute inhabitants ; and it may be fairly 

 presumed that, as in the case of the Fungi, the dried cysts or germs 

 of Infusoria are everywhere floating about in the air, ready to de- 

 velop themselves wherever the appropriate conditions are presented ; 

 but we must remember that but few definite observations have 

 been made as to the length of time these cysts will survive desiccation ; 

 at present, the observations of Nussbauni and Maupas make the 

 limit less than two years. 



Gruber has recently reinvestigated the process of conjugation in 

 the Infusoria : he finds that the nucleolus of each becomes a striated 

 spindle, and approaches the nucleolus of the other cell; the two 

 touch and finally fuse, thereby effecting an intermixture of the 

 different germ-plasmas. If this be the correct manner of interpret- 

 ing the phenomenon, it is clearly comparable to the sexual reproduc- 

 tion of multicellular animals. 



There can be no doubt as to the occurrence of 'conjugation' 

 among ciliated Infusoria ; and this not only in the free-swimming, 

 but also in the attached forms, as Stentor (fig. 594, 3). Iri 

 Vorticella, according to several recent observers, what, has been 

 regarded as gemmiparous multiplication the putting forth of a bud 

 from the base of the body is really the conjugation of a small 

 individual in the free-swimming stage with a fully developed fixed 

 individual (microgamete) with whose body its own becomes fused. 

 But it is doubtful whether such conjugation has any reference to the 

 encysting process. According to Biitschli and Engelmaim, the con- 

 jugating process results in the breaking up of the nucleus and (so- 

 called) nucleolus of the conjugating individuals ; these individuals 

 separate again, and after the expulsion of the broken-up nuclear 

 structures the characteristic nucleus and nucleolus are re-formed. 

 There is still much uncertainty in regard to the embryonic forms of 

 ciliate Infusoria, some eminent observers asserting that the 

 ' gemmule ' in the first instance, besides forming a cilia-wreath, puts 

 forth suctorial appendages (fig. 594, 1, A, B, C), by means of which 

 it imbibes nourishment until the formation of its mouth permits it to 

 obtain its supplies in the ordinary way ; whilst others maintain these 

 acinetiform bodies to be parasites, which even imbed themselves in 

 the substance of the Infusoria they infest. 1 



It is obvious that no classification of Infusoria can be of any 

 permanent value until it shall have been ascertained by the study 

 of their entire life-history what are to be accounted really distinct 



1 There can be no doubt that Stein was wrong in his original doctrine that the 

 fully developed Acinetina are only transition stages in the development of Vorti- 

 cellina and other ciliated Infusoria. But the balance of evidence seems to the writer 

 to be in favour of his later statement, that the bodies figured in fig. 594, i, are 

 really infusorian embryos, and not parasitic Acinetee. 



