OP ARTS AND SCIENCES. 17 



Professor J. Wyman said that he had recently had an 

 opportunity of examining a human foetus of the very early 

 period of from the twentieth to the twenty-fifth day from 

 conception. There were many points in its structure at that 

 time which corresponded to the permanent condition in some 

 of the lower animals. Some of these he proceeded to point 

 out, illustrating his remarks on the blackboard. The eyes 

 were found at this stage of development very far apart, in a 

 position on each side of the head, similar to that which is per- 

 manent in fishes and some of the lower mammals, and very 

 small. The mouth and nostrils formed but one cavity, which 

 would be divided off subsequently by the growth from above 

 and on the sides. It was evident that the deformity known 

 as " hare-lip " is only an arrest of development at this stage. 

 The lateral position of the nostrils is like that which is seen in 

 some of the adult monkeys of the New "World. The bran- 

 chial fissures, resembling the gill-openings in fishes, are also 

 visible at this early period, and one of them is known occasion- 

 ally to remain at maturity. The extremities were merely in a 

 rudimentary state, corresponding to what is sometimes seen 

 in a certain class of monstrosities after birth. A rudimentary 

 tail also existed, turning upwards towards the abdomen, and 

 extending considerably beyond the rudimentary legs, subse- 

 quently to be surrounded and concealed by the downward 

 growth of these extremities and the pelvis. Professor Wyman 

 also stated a fact, which he thought had not been heretofore 

 noticed, that the yolk-sac grows and forms new granules some 

 time after the development of the foetus has commenced. 



Professor Agassiz referred to a subject which had puzzled 

 both botanists and zoologists, — the question of individuality. 

 "What constitutes an individual ? He spoke of the various 

 opinions of botanists on the subject, showing how diflicult 

 it had been to distinguish between individuals and organs. 

 Professor Braun considers independent axes in plants as con- 

 stituting independent individuals. The same question has 

 divided zoologists. Corals have by some been regarded as 



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