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 eurojiteus, Schr., and 

 Buthus afer, L. Grenacher's investigations ('80, p. 42) were made upon 

 Buthus afer, Ischnurus caudicula, and Lychas americanus. Androctonus 

 funestus, var. citrinus, Ehr., Euscorpius italicus, Roess. and E. 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 Centrums.* 

 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. S. 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 otf the chitine around the eyes, and 

 cutting the retina and the lens after the removal of as much chitine as 



e. 

 Tlie pigment is so abundant and so dense that even the thinnest sec- 



* I am unable to state what species tins is. I have not succeeded in finding 

 it described anywhere. Specimelis in the collection of the Museum marked bj' 

 Simon as "Centrurus sp. incog." are of the same species as those here described. 



