ZOOLOGY. 



343 



ance of Gregarina in the ventriculus of Julus margmatus. Gregarina 

 has recently attracted much attention, as being supposed to be an ani- 

 mal consisting only of two cells, and said by Diebold to be destitute 

 of an alimentary canal. Dr. Leidy describes a papilla surmounting 

 the superior cell, with traces of an external communication with the 

 cavities of the cells. He regards it as the larva of the entozoon. 

 Proceedings of Academy of I\aiural Sciences, Phil. 



ON THE PHYSIOLOGY OF GENERATION. 



AT a meeting of the Boston Society of Natural History, in March, 

 Dr. Burnett read a paper on the embryology of Articulate', as illustrat- 

 ing some obscure phenomena in the physiology of generation. In the 

 formation of the extremities of insects, a process takes place similar 

 to that of the first stages of development of the whole body. As the 

 whole body was at first a cylindrical blastemal mass, subsequently 

 marked by transverse grooves indicating its articulated character, so the 

 limbs are primarily cylindrical tubes, afterwards divided transversely 

 into different joints. The true typical characteristics of species belong 

 to the primitive ovum ; and consequently 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 wrings of insects are 

 only expanded tracheae, and consequently belong to their primitive 

 characteristics, 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. Some singular facts are 

 observed in the generation of the bumblebee and aphides. In the for- 

 mer 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 consistent with the 

 highest and most philosophical view T s of the essential nature of genera- 

 tion. He explained the process, which he had observed, of the divis- 

 ion of the sperm cell by which the spermatozoon is produced, describ- 

 ing it as similar to the division of the ovum in the female. The 

 function of the spermatozoon is 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 kno\vn as the pro- 

 cess 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 platinum. As 

 the particles of magnetized iron have the power of transmitting to 

 others, by mere contact, the property communicated to them, so the 

 cells of the ovum, being, so far as is known, in their nature precisely 



