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articulated character, so the limbs are primarily cylindrical tubes, 

 afterwards divided transversely into different joints. 



Dr. Burnett expressed the opinion, that the true typical char- 

 acteristics of species belong to the primitive ovum ; and conse- 

 quently little weight should be given to the theory of the change 

 of such characters, or the introduction of new ones by external 

 influences. Thus, as the wings of insects are only expanded 

 tracheae, and consequently belong to their primitive character- 

 istics, their actual existence might have been predicated at an 

 earlier period than they had been supposed to exist before the 

 recent investigations of Burmeister and Agassiz. 



Dr. Burnett spoke of the singular facts observed in the gener- 

 ation of the Humble Bee and Aphides. In the former, three 

 successive broods of offspring are produced from one act of 

 impregnation ; the first brood, he believed, being alone produced 

 from eggs directly impregnated. In the Aphides, a succession 

 of broods is produced, sometimes to the number of ten or 

 eleven, each being the offspring of the preceding, and all the 

 result of the impregnation of the parent of the first. 



Dr. Burnett proceeded to examine Owen's and Steenstrup's 

 views as to the nature of the process by which this succession of 

 generation was effected, stating that they did not accord with his 

 own. He thought the phenomena were not anomalous, but con- 

 sistent with the highest and most philosophical views of the 

 essential nature of generation. He explained the process, which 

 he had observed, of the division of the sperm cell by which the 

 spermatozoon is produced, describing it as similar to the division 

 of the ovum in the female. The function of the spermatozoon 

 was to awaken, by contact, the slumbering force which led to the 

 formation of the embryo in the ovum, — a process similar, he 

 thought, to that in the inorganic world known as the process of 

 catalysis, as in the instances of the immediate magnetizing of 

 iron by contact with a magnet, and the production of water from 

 a union of hydrogen and oxygen by the contact of spongy pla- 

 tinum. As the particles of magnetized iron have the power of 

 transmitting to others by mere contact, the property communi- 

 cated to them, so the cells of the ovum, being, so far as is known, 

 in their nature precisely similar to each other, may in certain 

 instances be supposed to be able to communicate to another 

 ovum the force which has spread to them all, from the contact of 



