180 PROFESSOR E. RAY LANKESTER AND A. G. BOURNE. 



the lateral eyes of Limulus. It is to be regretted tliat the 

 sections used by Dr. Packard were not made transparent 

 before they were put under the microscope and drawn. 



Material. — We have studied the central and lateral eyes of 

 two species of Scorpion, viz. And roc ton us funestus, var. 

 citrinus, Ehr., obtained in the living state by Prof. Lankester 

 from North Africa, through the kindness of Prof. Carl Vogt, 

 and of Euscorpius Italicus, Roess. (also of the allied E. 

 Carpathicus), kindly forwarded to us in the living state by 

 Mr. Carmichael Gibson, and by Mr. Neville Reid, from the 

 South of Italy. 



We have been able from time to time to purchase living 

 specimens of the American King-crab, Limulus poly- 

 p hem us, Latr,, in London, though we have felt here very 

 much the want of small specimens not exceeding one or two 

 inches in the diameter of the prosomatic shield, which would 

 have been easier to cut and in other respects advantageous. 



Methods. — We have been able to ensure, as above shown, 

 the perfect freshness of the material used. 



The soft tissues of the eye were placed, with the piece of 

 chitinous cuticle adjacent, in absolute alcohol. In the case of 

 the central eye of Limulus it was found necessary to separate 

 the soft tissues from the chitin before immersion in alcohol. 



Sections were prepared by the method of long soaking, first 

 in turpentine then in paraffin, and slicing with the improved 

 Riviere's microtome. Most of the sections were then, after 

 removal of the paraffin, carefully depigmented whilst under 

 observation by the use of dilute nitric acid (about 5 to 10 per 

 cent,). The process of the destruction of pigment was ar- 

 rested at various stages. Some of the depigmented sections, 

 and some of those not treated to remove pigment, were stained 

 with borax carmine and mounted in Canada balsam. Others 

 were ])reserved in glycerine unstained. 



We may point out that the excellent method of thorough 

 impregnation with paraffin enabled us to obtain exceedingly 

 thin sections of the Scorpion's eyes, and to preserve complete 

 series for study. 



