248 



coalescence of piles of cells into one continuous whole, as has 

 been noticed by Barry and Toynbee. 



2. In the Oviparous Vertebrates. In the embryo of the 

 Chick the phases of formation are best studied about the eighth 

 day. Here, as in the previous instance, the opaque central part 

 is granular and cellular, and the peripheric portion tubular or 

 soon to become so. The minute vesicles are observed gradu- 

 ally expanding, until they have reached a certain size, when they 

 become nucleated ; thus presenting the appearance of nucleated 

 and non-nucleated cells. When they have become nucleated they 

 begin to arrange themselves into rows, one cell after another, and 

 then by coalescence form a tube. There is this difference, how- 

 ever, in the process, as it takes place in the Goat and the Chick, 

 that in the former several rows of cells form a tube, in the latter 

 one row only ; and extended observation renders it probable that 

 this difference between the Oviparous and Mammalian Verte- 

 brates in the process of fibre-development is something more 

 than a casual one. Afterwards the nuclei of these metamor- 

 phosed cells gradually disappear, and beautiful transparent fibres 

 are the result. 



By this description it will be seen that the phenomena of this 

 metamorphosis are of the same character as those involved in 

 the formation of muscular fibres ; that is, a kind of intus-suscep- 

 tion, and not, as Schwann thought, an immediate fibre transition 

 of cells. 



Dr. Durkee remarked, that he had frequently seen numerous 

 cells of various sizes, even in the adult human lens. 



Dr. Burnett said, that these were probably diaphanous vesiclesi 

 without nuclei, known to microscopists generally, and mentioned 

 by Schwann. They might have been nucleated cells, the 

 nuclei of which were transparent and very near to the cell wall, 

 making it extremely difficult to see them. The proper diapha- 

 nous vesicles might occur in any organizable fluids. 



The Secretary presented, in behalf of Mr. W. O. Ayres, 

 descriptions of two new species of Ophiuridse with the 

 names Ophiothrix hispida, and Ophiolepis uncinata, as fol- 

 lows : — 



Several species of Ophiuridae, brought by Mr. Stimpson from 



