No. 3. — Ariiitosis in the Eiiibryonal Envelopes of the Scorpion. 

 By H. P. JoHNSON.i 



In the fall of 1889, at the suggestion of my instructor, Prof E. L. 

 Mark, I decided to work upon the problem of the so-called " direct " or 

 amitotic division of nuclei. While in search of suitable material, my 

 attention was called to a brief article by Blochmann {^^5), describing a 

 very well marked amitotic division for the large nuclei of the embry- 

 onal membrane of the scorpion. A number of Centrums embryos 

 ■were kindly given to me by my friend, Dr. G. H. Parker. These em- 

 bryos had lain in 90% alcohol since the summer of 1886. The mode 

 of fixation (for the purpose of studying the development of the eyes) 

 was somewhat unusual ; for, immediately after their removal from the 

 mother, they were immersed in 35 <^ alcohol, and thence carried up 

 quite rapidly, through 50 and 70%, to 90%. Xotwithstauding this 

 rather crude method, the membranes were in excellent histological 

 condition, in no way inferior to material afterwards prepared by the 

 most approved methods of fixation. 



In addition to the material above mentioned, I received fi'om Mr. 

 Eichard Goeth, of Burnet County, Texas, during the following winter 

 and spring, about three dozen live specimens of Centrums (sp. incog.). ^ 

 A lot that arrived in the latter part of May contained several pregnant 

 females, witli embryos in different stages. The scorpions were chloro- 

 formed, and the ovarian tubes with the embryos enclosed were dissected 

 out as quickly as possible. A number of killing agents were used, 

 including Flemmiug's weaker chrom-aceto-osmic, Piabl's chrom-formic, 

 Perenyi's fluid, Kleinenberg's picro-sulphuric, and Merkel's fluid. 



For staining, T have used chiefly Ehrlich's hsematoxylin. Grena- 

 cher's alcoholic borax-carmine and Czokor's alum-cochineal have given 

 fair results. Safrauin, employed according to Flemming's method, I 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology, under the direction of E. L. Mark, No. XXX. 



2 This is the species used by G. H. Parker in his study on the development of 

 the eyes (see Bull. Mus. Comp. Zool., Vol. XIII. No. 6, p. 173, 1887), and was then 

 nndescribed. I am not aware that it has since received a name. 

 VOL. xxir. — NO. 3. 



