REPRODUCTION IX THE INFUSORIA. 289 



These spermatozoa, at all periods of their evolution, were 

 quite motionless. 



Water and most other reagents exert a rapidly destruetive 

 influence on the spermatic capsules. 



While the development of these capsules is in progress they 

 undergo considerahle changes of position, gradually with- 

 drawing from the ovarian segments to which they were, at 

 first, so closely approximated. As to the arrangement which 

 they eventually assume, no two individuals precisely resem- 

 ble one another in this respect. M. Balbiani, however, 

 infers that they still, as before, remain protected by a com- 

 mon envelope. 



After each sexual act the capsules become much smaller, 



and more or less altered ; their contents, by degrees, becoming 



wholly absorbed. At length they disappear in toto, Avhile, 



■ as yet the fertilized eggs remain within the body of the 



parent. 



Among other Infusoria, the development of the male organ 

 takes place in a manner more or less similar to that of the case 

 just cited. Usually the number of male and female elements 

 corresponds. "Thus, ChUodoii produces but one egg and 

 one spermatic capsule. In Stylonycliia Mytilus, Urostyla 

 Weissei, &c., the sexual elements are four in number, respec- 

 tively. One of the most remarkable cases in this regard with 

 which we are acquainted is that of Spirostomum anibiguum, 

 in which each of the forty fragments which, at the time of 

 reproduction, make up the long chaplet of eggs in this 

 species, bears, attached to its surface, a minute corpuscle, 

 which only becomes visible at this period, and which repre- 

 sents the corresponding male element.^' 



Occasionally, however, the number of male and female 

 elements is not equal. " The case w^iich most frequently 

 occurs is that Avhieh is expressed by the ratio 4 : 2, the first 

 term representing the female, the second, the male elements. 

 This ratio affords a mathematical demonstration of the mode 

 in which each order of elements is produced, by means of the 

 binary division of an element primitively simple [Oxytriclia, 

 Stylonyclda j)ustulaia, Kerona polyimrum) .^ But greater 

 numerical differences may occur. Thus, one species g^ Para- 

 mecium has at least twenty eggs, and but two or four sper- 

 matic capsules. And in two other forms of the same genus 

 (P. aurelia and P. bursaria) the contents of these capsules 

 are developed in a curiously exceptional manner, the details of 



* " It is not uncommon to see the male element subdivide itself twice, 

 like the female element, the numerical equality of their determinate pro- 

 ducts being thus again restored." 



