Antithetic Alternation of Generations. 445 
deep fundamental similarity between the modes of repro- 
duction and development of animals and of plants. 
Although regarding Metazoan development as a sort of 
apospory, I did not at first foresee the obvious result of 
a suppression of spore-formation, and it is due to my pupil, 
Mr. J. A. Murray, B.Sc., to state that it was he who first 
recognized how the omission of a spore-formation in animal 
(i. e. Metazoan) reproduction would affect the position where 
a reducing division could take place. All that had been 
done in upwards of seven years was needful before this final 
comparison of animal- and plant-reproduction could be drawn, 
and the possibility of its accomplishment appears to me to 
form the crowning point which proves the edifice to be fairly 
complete. Not only that ; the sequel will, I venture to 
think, show the foundation on which so much labour and 
time have been expended to be correctly laid. The main 
point, at which attack may appear to be still possible, 
will undoubtedly be the evidence on which the occurrence 
of an antithetic alternation of generations in animals is 
based. 
Those who think no sort of proof is possible may perhaps 
be astonished to find how mistaken was their belief, when 
all the evidences are laid before them. In one paper, or 
indeed in half a dozen, this cannot be satisfactorily done. 
Life is too short and time too limited for the individual, 
overwhelmed with other duties, to entertain any hope of 
being able, from his own observations, to demonstrate such 
an alternation in every group of the animal kingdom. 
My own investigations 1 have hitherto been almost ex- 
clusively limited to the group with which I am most familiar, 
and in which, as it happens, the evidences in current em- 
bryology are least apparent, viz. the Vertebrata. For other 
forms, in the meantime, recourse must be had to the work 
of others, and this, if too often deficient from my point of 
view, is the more valuable in that such observations as do 
1 A memoir, many of whose results and conclusions are assumed in the present 
