Nos. 455-456.] 



FASCIOLARIA. 



871 



were multiplying by amitosis, the simpler mode having been 

 adopted for local reasons. 



The material on which this paper is based was collected at 

 Beaufort, North Carolina (Osborn, '85), and preserved in either 

 cold aqueous corrosive sublimate, picronitric or chromic acid 

 solution. Sections were cut serially and stained on the slide in 

 borax-carmine, in the days before iron-haematoxylin had been 



discovered. I should have been glad to check these results l)y 

 more recent methods had access to fresh material been possible ; 

 however, the technique is fairly adequate for my purpose, as 

 shown by the condition of the mitotic nuclei present and many 

 other delicate cytological details. A brief account of the struc- 

 ture of the embryo will facilitate orientation, especially as this 

 form is considerably aberrant. My studies at Beaufort were 

 broken off before I had gotten the earliest stages. Sections of 

 my earliest embryo are shown in Figs, i and 2. It is already 

 past the gastrula stage, and consists of an extremely attenuated 

 ectoderm enclosing a great number of small spherules .each of 

 approximately 0.15 mm. in diameter. There is a throat and a 

 small amount of ectoderm, not nearly enough to enclose the 

 spherules. The spherules are made up of a small mass of cyto- 



