“168 THE ORCHID REVIEW. (JUNE, 1915. 
-of which is that cells of two kinds are produced, which agree in having only 
half the normal number of chromosomes, and are incapable of developing 
further until a process has taken place by which the original number of 
chromosomes has been restored. In the simplest forms of water plants the 
two kinds of sexual cells are borne separately, and unite by a process of 
-conjugation, the male cells being ciliated and reaching the female by 
-swimming, when the nuclei of the two cells fuse together, and form the 
initial stage of the new organism. From this simple stage they proceed 
through a process of ever-increasing complexity to the production. of pollen 
-and ovules, culminating in such floral complexities as are seen in the most 
highly specialised Orchids. Through all multitudinous ramifications there 
‘is a purpose. They are adaptations which have been brought about under 
changing conditions by means of the evolutionary process, which has 
-secured the survival of beneficent variations. And they are largely 
connected with the habits of their insect guests. 
But whatever the complexity by which the union of the sexual, cells is 
-brought about, the subsequent process is identical, and the two conjugating 
‘nuclei each bear their own half of the hereditary qualities. This is well 
-seen in the case of hybrids, where nuclei from two parents bearing a 
number of distinct characters combine to form a complete blend, whereby 
what is termed an intermediate hybrid‘is produced. When the hereditary 
-qualities of the two cells are alike, as in the case of normal fertilisation by 
pollen from the same species, this character of the union is not obvious, and 
-all that is seen is the stimulus which the act of fertilisation gives to the 
-development of. a new individual. It nevertheless -carries with it 4 
multitudinous series of events that can best be imagined from the remark- 
-able behaviour of a batch of secondary hybrids such as those with which we 
-are already familiar. The case of Cattleya Sibyl has already been 
mentioned, and several striking examples in the genus, Odontioda and 
-others have been described. Little as is certainly known about the process 
this much may be said, that they are controlled by the ramifications of the 
nucleus in the germ plasm. 
This is only the briefest possible summary of the processes sivolueds 
-and it shows that the characters of the each sexually-formed individual are 
derived from a mixture of two individually distinct germ plasms in the act 
-of fertilisation. It also shows where Darwin’s highly ingenious hypothesis 
of Pangenesis fails, but it does not exclude the idea of the existence of 
formative gemmules developed in another way. Nor yet does it follow that 
‘the two germ plasms which unite are themselves immune from all external 
influences. It is certain that there is a progressive development of new 
characters, otherwise evolution would not be possible. But this and the 
-question of reversion must be left for a future article. 
