ON BIOLOGICAL ANALOGIES. 269 



The phenomena of reproduction in animals and plants present 

 many features worthy of comparison. It is scarcely rash to say 

 that sexuality is as common and universal in the vegetable as in 

 the animal kingdom. Not many years ago such an assertion could 

 scarcely have been ventured upon with confidence, when the re- 

 production of the lower cryptogamia was so little known, but every 

 new discovery adds strength to a belief in universal sexuality. The 

 completeness of the sexual organs and their functions is not a 

 matter of mere speculation. The male and female organs are 

 definite and distinct. They approach each other, as it were, in- 

 stinctively, and unite. The ovary receives the contents of the 

 antheridium, which, in many cases, are multitudinous active sper- 

 matozoa, with a remarkable similarity to the same bodies high up 

 in the zoological scale. The opening of the ovary just as the sper- 

 matozoids are matured, as in the genera OEdogonium and Vancheria, 

 the entrance of these and their absorption, and finally the maturing 

 of the fertilized ovum, are notable analogies. If we seek more 

 special and particular examples these can be found. What, for 

 instance, could be more suggestive of the fusion which takes place 

 in some of the Infusoria, in which two individuals meet, collide, and 

 finally coalesce in one individual, than the conjugating zoospores in 

 Botrydium granulatum, where two active zoospores unite, and by 

 their union become a true fertilized isospore, in which all motion 

 soon comes to an end, and is followed by the development of a young 

 plant like its original parent. These are some of the phenomena 

 which startled certain of our progenitors into the supposition that 

 infusoria were generated within, and ultimately escaped from, the 

 tissues of living plants. 



Metamorphosis, such as we are acquainted with in insects, has 

 also its analogue in the vegetable kingdom. From the egg of a 

 butterfly emerges, not a form like the parent, but a caterpillar, which 

 passes through a period of existence and then comes to rest ; it 

 changes into a pupa or resting condition, in which it remains for a 

 more or less lengthened period, then its final change takes place, 

 and the perfect imago appears, the true image of the original parent. 

 In some of the lower plants we may recognise a similar meta- 

 morphosis. In some of the Myxogasters, for instance, the spore, 

 which is the ovum or egg, produces a larval form, an active zoospore. 

 After a time this becomes amoeboid, more sluggish, and quite 

 different from either zoospore or parent, and finally from the 



