REPRODUCTION IN THE INFUSORIA. 291 



least) a four-fold character ; that is, histological, in its con- 

 nection with the subject of egg-formation in general; zootom- 

 ical, so far as it suggests data for comparison with the 

 organs of reproduction in other animal tribes ; practical, as 

 showing how much may be effected in a certain class of 

 investigations,, by patience combined with the right use of 

 reagents ; and phifsiological, from its bearing on the im- 

 portant question of fertilization in bisexual organisms. 



The past season has seen the production of Mr. Darwin^s 

 new work on the ' Fertilisation of Orchids/ in which he has 

 set forth^ with much skill and interesting detail, the various 

 and often highly complicated contrivances by which, among 

 this extensive group of hermaphrodite plants, self-fertilisation, 

 save in a very few exceptional instances, is rendered abso- 

 lutely impossible. For the ovary of one Orchid is fertilised 

 by the male element of another, and to affect the junction of 

 these the intervention of insect agency is necessary. The 

 case of the Infusoria is, in some respects, comparable, even 

 though with them such foreign intervention be wanting. 

 Like Orchids, they are hermaphrodite, but not self-fertilising, 

 their fecundation being effected by constantly dissimilar 

 elements produced in different individuals. And in both 

 cases, this contact cannot take place without the pre\dous 

 occurrence of a process more or less complex, the details 

 of which are curiously varied in their several tribes. Theo- 

 retically, notliing seems easier than for an Infusorium (or 

 Orchid) to fertilise itself. There are indeed some Infusoria 

 in which, so far as we at present know, the act of sexual 

 union appears impossible. May it not be that these are 

 capable of self-fecundation, just as, in this very respect, 

 a few Orchids differ from the great majority of their order. 

 Here, as elsewhere, the exception proves the rule; and 

 such exceptions, while they forbid the systematist to dogma- 

 tise, and warn him never to neglect the final process of 

 verification, are full of meaning for the philosophic student 

 of biology. By these nature, so to speak, points out to us 

 the simpler method, Avhile in practice she adopts another, 

 attended with much delay and apparent diflSculty. But not 

 without a purpose. And, perhaps, in this particular case the 

 lesson which she seeks to convey is that which has been so 

 well expressed for us by Mr. Darwin : " It is an astonishing 

 fact [among Infusoria as well as in Orchids] that self- 

 fertilisation should not have been an habitual occurrence. It 

 apparently demonstrates to us that there must be something 

 injurious in the process. Nature thus teUs us, in the most 

 emphatic manner, that she abhors perpetual self-fertilisation 



