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Prof. II . C. Bastian on Heterogenetic [Mar. 21, 



of the mode of origin of such larger organisms as Paramecium and Kolpoda. 

 Although their most remarkable mode of origin was fully described and 

 figured by M. Pouchet more than twelve years ago, yet, unfortunately, 

 many of our leading biologists have preferred to repudiate his statements 

 and rely upon their own notions concerning credibility and the mode in 

 which living matter ought to conduct itself, rather than adequately inves- 

 tigate the subject for themselves. 



According to Pouchet, the stages in the evolution of Paramecium viride 

 were as follows : — The pellicle, which was at first uniform and evenly gra- 



Fig. 7. — Mode of Origin o/* Paramecia from the Pellicle\ after 

 Pouchet. (x400.) 



nular, after a short time changed in aspect here and there, owing to a con- 

 centration of its granules at tolerably equal distances into small, more or 

 less rounded aggregations, which soon became surrounded and defined by a 

 clear border, suggestive of a resemblance to the zona pellucida of higher 

 animals. The next change which took place was, that the granules, which 

 had been at first more densely aggregated towards the centre, disseminated 

 themselves uniformly through the ovum, whilst at the same time the 

 simple clear zone thickened into a distinct membrane. At this stage the 

 whole egg appeared somewhat lighter and more transparent than the sur- 

 rounding pellicle. Soon after this, differentiation still proceeding, the 

 mass of enclosed granules gradually became converted into a real embryo, 

 which manifested its existence by slow movements — at first by simple 

 oscillations in the mass of granules, and afterwards by regular uniform move- 

 ments of revolution of the whole contents within its enveloping membrane, 

 similar to those of many other embryos. The slightest shock at this stage 

 immediately arrested the gyration. Then, after a time, a pale spot appeared 



