Dr. C. F. J. Lachmann on the Organization of Infusoria. 237 



conditions, the embryos were probably converted into VorticelltB, 

 I therefore endeavoured to ascertain this also, and for this pur- 

 pose isolated at different times a number of individuals of the 

 large Acineta ferrum-equinum, Ehrbg., which were perceptible 

 even with the lens, in a small glass tube, as I had isolated Vor- 

 ticellce in other cases. In order that they should not be in want 

 of nourishment, I put a number of individuals of Paramecium 

 Aurelia and P. Bursaria with them in the tube, and to preserve 

 the water in a good state, also placed in it a Lemna minor. 

 These experiments required the greatest care, and their difficulty 

 is a sufficient explanation of my not having obtained clear results 

 in all cases. Thus in one case I found two specimens of Vorti- 

 cella campanula in one of my glasses, when I came to look at it 

 again in eight days ; in another I found several of the Vorticella 

 nebuUfera without a single V. campanula. This difference of the 

 Vorticella discovered must show at once that they had only got 

 in by accident, and had not been developed from the embryos of 

 the Acineta. How difficult it is to avoid such an accident, was 

 proved to me by a case in which I had placed some Acineta in a 

 glass tube, and thought that I had convinced myself of the ab- 

 sence of any Vorticellina ; and yet, on again examining it with 

 the lens, I discovered, under the leaf of Lemna which had been 

 put in, a large Vorticella campanula, which I of course took care 

 to remove immediately. Two experiments, however, gave me a 

 perfectly clear result. One of these was given up at the end 

 of a week, but the other was continued for seven weeks, during 

 which the contents of the glass tube were frequently examined, 

 partly with the lens and partly with the microscope; but in 

 both I never obtained a single Vorticella, but only a considerably 

 increased number of Acinetce. The number of the latter was 

 also augmented in the other experiments, which did not give a 

 pure result. 



The preceding statements appear to me to furnish sufficient 

 proof that Stein^s opinion of the relationship of the Vorticellina 

 and Acineta is not only completely destitute of any real founda- 

 tion, but even, as an hypothesis, extremely improbable. I must 

 be excused if I have dwelt too long upon this theory; but 

 it appeared to be well worth a thorough examination, as it in- 

 troduced into science a perfectly new mode of propagation, which 

 could not be referred to any of the known modes of reproduc- 

 tion, not even to the alternation of generations ; and it was cer- 

 tainly high time to apply the standard of a fundamental criticism 

 to it, as it has unfortunately been already regarded by many as a 

 fact ascertained with certainty. An alternation of generations of 

 the kind hitherto known in other animals cannot be recognized 

 in the alternation of the modes of reproduction of the Infusoria, 



