188 Professor Owen on the ireneration of the 



with a specific character, as independent and distinct in its nature as 

 that of the highest and most complicated organisms. No mere organic 

 cell, destined for ulterior changes in a living organization, has a mouth 

 armed with teeth, or provided with long tentacula. I will not lay stress 

 on the alimentary canal and appended stomachs, which many still re- 

 gcird as '^ sub judice ;" but the endowment of distinct organs of genera- 

 tion, for propagating their kind by fertile ova, raises the Polygastric 

 Infusoria much above the mere organic cell. 



In many of the larger species of Polygastria, radiated vesicles, sub- 

 transparent and colourless, generally two in number, and situated near 

 the two extremities of the body, of a highly irritable nature, rapidly 

 contracting and dilating, have been observed. Boesel first figured this 

 contractile vesicle in the Vorticella. In Enodon, in addition to these ve- 

 sicles, Ehrenberg likewise discerned another organ, of an oval shape, of 

 a dull white colour, and of considerable size, placed in the middle of the 

 abdomen. It is easily detected by the Avant of colour, when tlie animal 

 has been well fed and its stomach filled. This organ is regarded as the 

 testicle, and the contractile radiated bladders as the Vesiculcs Seminales. 

 The ovarium occupies a more important share of the general cavity of 

 the bod}-. It fills all the interspaces of the stomachs and intestine 

 which are not occupied by the male organs, and consists of a number of 

 minute corpuscles, or nucleated cells, connected together in a reticulate 

 form, generally of a green or pink, or some other bright colour, in well- 

 fed healthy Polygastria. 



The act of generation is attended with the destruction of the parent. 

 The ripe ova burst through some part of the abdominal integument, 

 and escape in a reticulated mass, together with the fertilizing fluid. 



By virtue of these diversified modes of multiplication, the powers of 

 propagation of these diminutive organized creatures may be truly said 

 to be immense. Malthusian principles, or what are vulgarly so called, 

 have no place in the econom}- of this department of organized nature. 

 To the first great law imposed on created beings, '• increase and multi- 

 ply," none pay more active obedience than the Infusorial animalcules. 



Attempts have been made to calculate approximately this rate of in- 

 crease. 



On the 14th of November, Ehrenberg divided a Paramcccium aurclia, 

 a Polygastric animalcule measuring one-twelfth of a line in length, into 

 four parts, which he placed in four separate glasses. 



On the l7th of November, the glasses numbered 1 and 4 each con- 

 tained an isolated pararasecium, swimming actively about. The pieces 

 in numbers 3 and 4 had disappeared. 



On the 18th there was no change. 



On the 19th each animalcule presented a constriction across the mid- 

 dle of the body. 



