237 



found their natural interpretation, for it was at once recognised that 

 the conclusions previously arrived at pointed to a sort of Apospory 

 in animal development. At the same time the problemof the nature 

 of the reducing division intruded itself, thanks to a presidential address 

 of Prof. Bower's ^) in which Strasburger's conclusions were discussed. 



It seemed necessary to find the explanation of this in animals, if, 

 as was more than suspected, there existed some deep fundamental 

 similarity betwen the modes of reproduction and development of ani- 

 mals 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 recognised 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 reproductiou 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 cor- 

 rectly 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 generation 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 evi- 

 dences 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 enter- 

 tain any hope of being able, from his own observations, to demon- 

 strate such an alternation in every group of the animal kingdom. 



My own investigations -) have hitherto been almost exclusively 

 limited to the group with which I am most familiar, and in which, 

 as it happens, the evidences in current embryology 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 



1) Botanical Society, Edinburgh, Nov. 1894. 



2) A memoir, many of whose results and conclusions are assumed in 

 the present paper, is now in the press. 



