Intus-susception and Reproduction. g 



"certain freedom not possessed by solids, but of late crystalline 

 '''liquids have been discovered which possess properties hitherto 

 "only encountered in solid crystals [p. .63]. ... It occasionally 

 "happens that when two substances are melted together, the 

 "liquid when cooled does not deposit one of the substances only 

 "but both at once. This generally occurs when the two solids 

 "crystallize in the same torm. Such homogeneous solid mixtures 

 "are often called solid solutions [p. 72], . . . and are in a sense 

 "comparable with liquid solutions, and one crystalline substance 

 "may be said to be dissolved in the other." [p. 212.] This is the 

 nearest approach to what Professor Schafer asserts that is contained 

 in Dr. Walker's treatise, and its remoteness from any process of 

 vegetable or animal growth needs no pointing out. The other 

 part of his assertion, that crystals multiply and reproduce their like 

 is even further apart from organic multiplication and reproduction. 

 Reproduction. 



There are three forms of reproduction in plants and in the lower 

 animals viz. Sexual, Vegetable or Asexual, [and Parthenogenetic. 



i. Sexual. Sexual reproduction is the nearly universal, the 

 most perfect, and the true form of the process. In this form, the 

 individuals of a species produce in different organs two comple- 

 mentary reproductive atoms, one male and the other female. Or 

 one individual may produce only the male reproductive bodies, the 

 female being borne on distinct individuals of the species. These 

 two complementary bodies are designed to meet and fuse together, 

 which action gives rise to what is known as an oospore or ovum. 

 In these ova, which are minute microscopic nucleated pieces of 

 protoplasm, the individuals of a new generation commence their 

 existence. Some biologists believe that without sexual reproduc- 

 tion, the evolution of so many distinct and numerous species, 

 genera, and families of either plants or animals could not have 

 taken place. I don't know that this opinion can be accepted 

 in full, for alteration of external circumstances seems a more 

 potent cause of variation. But it is certainly true that when a 

 plant I do not know about animals has established a number of 

 varietal forms, any or all of them may be reproduced by the differ- 

 ent seeds in the fruit, so that a parent, if a sexually produced 

 individual, inherits and may distribute all the specific characters. 



