206 Dr. L. Plate on the Oenus Acinetoides. 



to unicellular organisms, and therefore the free mobility of 

 the Acinetan offshoots must be regarded as a special pheno- 

 menon of adaptation. If there is really the tendency in the 

 organism to recapitulate in its ontogeny certain morphological 

 conditions which correspond in their sequence with the phylo- 

 genetic development, it is a matter of no consequence whether 

 these conditions are displayed by 07ie cell or by a cell-complex. 

 In the formation of buds in which the parent and its offspring 

 are even externally of such different structure, the micellar 

 structure of the plasma in the bud will very probably also 

 differ from that of the parent ; and it is quite conceivable 

 that the former agrees approximately with the plasmatic 

 structure proper to the ancestors of the Infusorian under con- 

 sideration, and therefore the biogenetic law may also apply to 

 the developmental history of the bud. This is impossible 

 only when a Protozoon divides into two portions which 

 behave exactly alike both as regards their external characters 

 and in their further phenomena of growth ; this, however, is 

 not the case in multiplication by buds. Suctoria of the 

 nature of the genus Acinetoides can be naturally referred only 

 to Ciliated Infusoria (whether directly or by the derivation of 

 both families from a common stock), and therefore the view, 

 which Maupas* has recently supj^orted, that the Acinetae are 

 more nearly allied to the Khizopoda, and especially to the 

 Heliozoa t; seems to me not to be correct. For if the sucking- 

 organs ot the Suctoria have really proceeded from Khizopod 

 pseudopodia, these ought always to be present in considerable 

 number, whereas in Acinetoides only one such tentacle occurs. 

 For the maintenance of Maupas's conception, therefore, we 

 must assume a reduction in the riumber of tentacles for the 

 genus just mentioned, a hypothesis which it is difficult to 

 reconcile with its other primitive characters. In support of 

 his hypothesis Maupas t cites a statement of Engelmann's 

 according to which tlie cilia in the lower plants and animals 

 are so diffused that in phylogenetic investigations no value is 

 to be attached to their presence or absence. I believe that 

 the above-mentioned naturalists go rather too far in their 

 deductions. It is certainly true that organs which, like the 

 cilia or eye-pigment-spots, recur in the most various classes, 

 are to be very cautiously made use of in phylogenetic ques- 

 tions ; but they are certainly not therefore wholly without 

 signiticance, for even their arrangement and position are 

 governed by heredity. It is only in this way explicable that 



• " Contribution a I'etude des Acinetiens," in Arch, de Zool. Exper. 

 tome ix. (1881), pp. 299-368. 



t Ibid. p. 367. J Ibid. p. 363. 



