12S 



BLIND VERTEBRATES AND THEIR EYES. 



uniform in shape in different individuals or even the two sides of the same indi- 

 vidual. It can be located and seen in cleared heads solely on account of the pig- 

 ment which is always abundant over the distal face of the eye. It is located so far 

 beneath the surface as to occasionally lie in contact with the brain case nearly 

 opposite the posterior end of the olfactory lobe. It has thus been withdrawn 

 much farther than in the other blind species. 



It is very much smaller than the eye of either T. snbterraneus or Amblyopsis. 

 Its size is, however, quite variable, measuring 40, 49, 56, 64, 54 by 96, 56 by 120 p. 

 in different instances, exclusive of choroid and sclcra. 



bruin 



eye 



I n:. j.j. (.j) Cross section of Part of Head of Trvgliflllliys, 25 mm. long, showing Position and 



lions of Eye. 



M Hr.nl .,( / ri:flii:hth\s from above, showing Relative Positions of Tactile Organs and Eyes. 

 Partol Same Head, showing Eyes with thi-ir Peculiar Pigmentation and Distribution 

 of Pigment Cells in Surrounding Tissues. 



Tlie muscles of the eye were in no case normal. I have not found more than 

 two rectus or more than one oblique muscle belonging to any one eye. They can 



' be made out from horizontal sections. In cross-sections it is very difficult to 

 identify or follow them. 



The besl developed rectus was found in a specimen 35 mm. long. It is com- 

 poseil of a number of normal fibers forming a bundle 20/1 in thickness, and from 

 it- origin to its insertion it is 2^6 ju, long. The remarkable peculiarity of this muscle 

 is that i oo /A of this is a tendon 4 /LI in thick ness (fig. 4(1 h,msc.r.}. The tendon spreads 

 into a cone -Imped mass of fibers attached to the proximal face of the eye. Traces 

 nl" two mu-( les were made out connected with the ricjlit eve of another individual. 



