Dr. C. F. J. Lachmann on the Organization of Infusoria. 233 



freely, generally in a form more or less differing from that of the 

 mother. Very different numbers of embryos may be formed in 

 one section of the nucleus ; in the same species we sometimes 

 find many and sometimes only one embryo formed in it; and 

 an embryo which has been developed alone in a fragment of the 

 nucleus is usually as large as all the embryos formed in a similar 

 fragment which has developed many of them, taken together. 



The true import of the nucleus of course is not decided by 

 this statement ; [we cannot say] whether it is to be regarded as 

 a germ-stock, in which germs are formed asexually ; as an ovary, 

 in which the ova are developed at the same time ; or, in accord- 

 ance with Focke^s views, as a uterus, in which the ova or germs, 

 formed in another place (perhaps in the nucleolus ?), are further 

 developed. 



The fate of the embryos which are unlike their parents, after 

 their birth, is still unknown in most cases. For the Acinetce, 

 Stein, as is well known, has set up a peculiar theory, which he 

 has endeavoured to support by many examples ; according to 

 this, the AcinetcB are metamorphosed Vorticella, which, in this 

 altered form, assist in propagation by the production of embryos; 

 the embryos, as Stein supposed, again became Vorticellce : un- 

 fortunately he never observed this directly, but always lost sight 

 of the embryos before their fate was decided. In support of the 

 transformation of the Vorticellce into Acineta, he brought for- 

 ward some supposed transitions, the series of which, however, 

 still presented considerable gaps. Many of these intermediate 

 forms, which are always encysted states, have so far distinct 

 characters, that they might also be referred as encysted states to 

 a great many other Infusoria, so that they can only furnish a 

 proof of the asserted transition, when we are certain that, in a 

 series of observations upon the transformation of one species, 

 we have always to do with the same individual, so as to exclude 

 the possibility of confounding individuals of other species there- 

 with. For, the reason, and almost the only one, that Stein 

 can adduce in favour of his opinion, in most of the Acineta, ex- 

 cept the analogy with the other AcinetcB, which led him to think 

 their relationship to the Vorticellce probable, — namely, the fre- 

 quent occurrence of certain Acinetce and Vorticellce in each other's 

 company, — is evidently no more a proof of relationship in this 

 than in other cases. The frequent parasitism of certain Acinetce 

 upon certain Vorticellince fm'nishes no better proof; we often find 

 other Infusorial parasites upon the same Vorticellince, so that we 

 have our choice as to which we will regard as related to the 

 host. 



In favour of the relationship between some Acinetince and 

 Vorticellinoe, Stein adduces an alternation in their occurrence ; so 



