XVIU PROCEEDTNGS OF THE 



encysted zooid, were scattered through the parenchyma ; and the 

 nucleus was not only distinct, but had increased considerably in 

 length. Round the whole a clear gelatinous envelope had become 

 excreted. 



In a later stage there was formed between the gelatinous envelope 

 and the cortical layer of the body a strong, dark brown, apparently 

 chitinous case, the surface of which, in stages still further advanced, 

 had become ornamented by very regular hexagonal spaces with 

 slightly elevated edges. In this state the chitinous envelope was so 

 opaque that no view could be obtained through it of the included 

 structures ; and in order to arrive at any knowledge of these it was 

 necessary to rupture it. The nucleus thus liberated was found to 

 have still further increased in length, and to have become wound 

 into a convoluted and comphcated knot. Along with the nucleus 

 were expelled multitudes of very minute corpuscles with active 

 Brownian movements. 



In a still further stage the nucleus had become irregularly branched, 

 and at the same time somewhat thicker and of a softer consistence ; 

 and finally it had become broken up into spherical fragments, each 

 with an included corpuscle resembling a true cell-nucleus, in which 

 the place of a nucleolus was taken by a cluster of minute granules. 



In this case the original nucleus of the vorticellidan had thus be- 

 come broken up into bodies identical with the so-called eggs of 

 Balbiani : but this was anaccompanied by any conjugation or by the 

 formation of any thing which could be compared to spermatozoal 

 filaments. 



What I believe we may regard as now established in the pheno- 

 mena of reproduction in the Infusoria is that, besides the ordinary 

 reproduction by spontaneous fission of the entire body, the nucleus 

 at certain periods, and after more or less change of form in the In- 

 fusorium-body, becomes broken up into fragments, each including a 

 corpuscle resembling a true cell-nucleus, and that this takes place 

 without necessarily requiring the influence of conjugation or the 

 action of spermatozoa ; that these fragments, after their liberation 

 from the body of the Infusorium, become developed (still without 

 the necessity of spermatic influence) directly or indirectly into the 

 adult form. 



Whether proper sexual elements ever take part in the life-history 

 of the Infusoria remains an open question. 



Everts* has given an account of observations which, with the 



* Everts, '■ Untersuchungen an Vorticella nebulifera" Sitziingsberichte der 

 physikaliseh-medicinisc'hen Societat zu Erlangen, 1873. 



