THE ANNALS 



ANl> 



MAGAZINE OF NATURAL HISTORY, 



[THIRD SERIES.] 

 No. 58. OCTOBER 1862. 



XXIV. — Contributions to the Natural History of the Infusoria. 

 By T. W. Engelmann*. 



[Plate III.] 



TuE author commences by noticing the rapid progress made, 

 during the last ten years, in respect of our acquaintance with 

 the structure of the Infusoria, and, in particular, the establish- 

 ment of the fact of sexual reproduction among them. He had the 

 advantage of pursuing his researches under the eye of Prof. Stein, 

 and procured the subjects for them in the neighbourhood of 

 Leipzig. 



Stein and Balbiani have both shown that among the Infusoria 

 there is an act of conjugation, and a sexual reproduction con- 

 sequent thereupon. For instance, they proved that during the 

 conjugation of two individuals, spermatozoa were developed in 

 the substance of the nucleolus, and that in all probability these 

 organisms penetrated the nucleus and gave rise to the formation 

 of germinal corpuscles and embryos. These observations were 

 made on the Paramecium aurelia and P. Bursaria ; and Engel- 

 mann is able to confirm their general accuracy. In two conju- 

 gated individuals of Paramecium Bursaria he observed the nu- 

 cleolus to be much enlarged, and to constitute two capsules, each 

 filled with rod-like corpuscles ; but, though he followed up his 

 examination of such conjugated forms until their separation, and 

 even subsequently, he failed to remark the development of em- 

 bryonic corpuscles. In one instance, conjugation was extended 

 to three individuals of Paramecium Bursaria, in two of which the 

 nucleus was much extended and band-like, whilst in the third it 

 retained its usual oval form. This triple conjugation he wit- 



* Abstract, by Dr. Arhdge, from the ' Zeitschrift fiir wissenschaftliche 

 Zoologie,' vol. xi. part 4 (1861). 



Ann.i^ Mag. N. Hist. Ser. 3. Volx. 17 



