174 BULLETIN OF THE 
paper on the development of the scorpion, barely alludes to the eyes. 
Their probable method of development is described by Patten (’86, p. 
672). His conclusions as far as they touch upon the eyes in scorpions 
are based upon inferences drawn from the method of development in 
other forms, not from actual observations. In a preliminary communica- 
tion by Kowalevsky and Schulgin (’86, pp. 530-532) the method of 
development for the median eyes is described at some length. On ac- 
count of incompleteness in their studies, these authors were forced to 
omit a description of the lateral eyes. Later in this paper, the substance 
of their communication will be considered. 
The species of scorpions previously studied have been numerous. 
Graber (79, p. 71) examined the eyes in Scorpio europeus, Schr., and 
Buthus afer, . Grenacher’s investigations (’80, p. 42) were made upon 
Buthus afer, Ischnurus caudicula, and Lychas americanus. Androctonus 
JSunestus, var. citrinus, Ehr., Euscorpius ttalicus, Roess. and £. carpathi- 
cus, were the species studied by Lankester and Bourne (83, p. 180). 
The embryological researches of Kowalevsky and Schulgin were made 
upon Androctonus ornatus. 
The species which I have studied belongs to the genus Centrurus.* 
In July and August, 1886, through Mr. C. W. Johnson, gravid females 
were obtained from Florida. At intervals during the following winter 
Mr. Johnson and Mr. F. 8. Schaupp of Texas supplied me with fresh 
material. I am also indebted to Dr. H. A. Hagen for some alcoholic 
specimens from Arkansas. 
In preparing the eyes for study by means of sections, the two chief 
difficulties encountered were the presence of chitinous lenses and dense 
pigment. It is difficult to cut the lens, and often this structure is in 
part torn away, thus destroying the surrounding tissue. In the median 
eyes, by careful dissection, the soft parts may be separated from the lens 
and cuticula, and cut without the interference of these hard structures. 
The separation is best accomplished after the tissues have been hardened. 
The method of dissection cannot be applied to the lateral eyes, for they 
are almost completely surrounded by chitine. In these eyes the best 
results were obtained by trimming off the chitine around the eyes, and 
cutting the retina and the lens after the removal of as much chitine as 
possible. 
The pigment is so abundant and so dense that even the thinnest sec- 
* IT am unable to state what species this is. I have not succeeded in finding 
it described anywhere. Specimens in the collection of the Museum marked by 
Simon as “Centrurus sp. incog.” are of the same species as those here described. 
