OF THE INSECTIVORA AND CHIROPTERA. 301 



cation is much less and amounts to not over one-third of the length, perhaps one-fourth; 

 the resulting crystal being then about two-thirds to three-fourths of the normal pyramid, 

 if complete and not truncated. In some cases the truncation is even more, so that the 

 crystal is about equidimensional. The basal surfaces were sometimes perfect, but more 

 often depressed as though the crystals grew more rapidly on the prism-base edges, and 

 the depression was frequently quite funnel-shaped. This was the common point of attack 

 for the bacteria, which converted the oxyhemoglobin to reduced hemoglobin as above 

 described. Twins of two types were noted: (a) interpenetrant twins on the second- 

 order pyramid (1123) (text figure 361) with the hexagonal axes inclined at 84 and 96 

 approximately, producing twins similar to those formed in quartz; (b) interpenetrant 

 twins on the third-order prism (text figure 362), which would seem to indicate that the 

 pyramid taken as unit may be a third-order pyramid and the twin a combination of the 

 plus and minus third-order pyramids with the principal axis coincident in the two members 

 of the twin. The exact orientation was not definitely determined in this case, however. 

 Pleochroism is strong; a =e, very pale red, nearly colorless; c=a>, deep red. Ex- 

 tinction is straight in all side views and the crystals are singly refracting on the base. 

 In convergent light a faint uniaxial figure is seen on the base. The axis of greatest 

 elasticity is the vertical axis c. Hence w > and the optical character is negative. 



Hemoglobin of Scalops aquaticus. 



Hexagonal, only observed in paramorphs after the oxyhemoglobin. The forms 

 and angles are hence identical in the two substances. The reduced hemoglobin para- 

 morph is produced by bacterial action. The bacteria enter at the basal depressions and 

 frequently penetrate the crystal from end to end, which then becomes like a short hex- 

 agonal bead with a central perforation. They work through the substance of the crystal 

 and completely honeycomb it, but usually leave a shell of unaltered oxyhemoglobin 

 on the exterior, including the pyramidal planes, but not the base, which is completely 

 eaten away. In some cases the crystals were thus completely converted to reduced hemo- 

 globin and the channels made by the bacteria were even repaired and filled up by re- 

 crystallized hemoglobin, making quite perfect crystals. 



Pleochroism was very strong, a=e, nearly colorless, pale lilac; c to, deep purplish- 

 red. The double refraction is strong and extinction straight. The axis of greatest 

 elasticity is the vertical axis, w > s; hence the optical character is negative, the same 

 as in the oxyhemoglobin. 



CHIROPTERA. 

 FOX-BAT OR FLYING-FOX, Pteropus medius. Plate 94. 



The specimen was received from the Philadelphia Zoological Gardens, 

 and was in a putrid condition. It was oxalated, a little ether added, and 

 preparations made as usual. The blood crystallized readily, and the crys- 

 tals did not appear to dissolve at first, but after a few hours they began to 

 break down and by the next day had disappeared from the slides. The 

 photographs were taken inside of 4 hours after the preparations were made. 

 The crystals were oxyhemoglobin. The examination of the crystals was 

 incomplete, owing to their disappearing from the slides so rapidly; and 

 hence the crystallographic constants were imperfectly determined. 



Oxyhemoglobin of Pteropus medius. 



Monoclinic (or perhaps triclinic): Axial ratio a : b : c =1 : 6 : 1.2808; /? = 5630'. 



Forms observed : Unit prism (110), orthodome (T01), clinopinacoid (010), base (001). 



Angles: The prism angle was not obtained. Hemiorthodome to prism edge or 

 orthopinacoid T01 A 100=50; hemiorthodome to base 101 A 001 =73 30'; ortho- 

 pinacoid to base (or prism-edge to base) 100 A 001 =56 30' =/?. 



