574 



SCIENCE. 



[N. S. Vol. XV. No. 380. 



ther studies of all these forms are now 

 being made. 



The Eye of the Common Mole: James 



ROLLIN SlONAKER. 



The eye of the mole lies imbedded in the 

 muscle beneath the skin, where it appears 

 as an inconspicuous dark spot. It is sit- 

 uated well forward on the side of the 

 snout. 



The eye is degenerate and is no longer 

 capable of functioning in distinct vision. 

 The most noticeable changes which have 

 occurred are: 



1. The great reduction in the size of the 

 eye. 



2. The much crowded condition of the 

 retina as a result of the decrease in size 

 of the eye as a whole. 



3. The noticeable reduction in the size, 

 or the complete absence of the aqueous 

 and vitreous chambers. 



4. The varied modification of the shape 

 and size of the lens. Also the peculiar 

 cell structure of the lens. 



All the structures of the normal mam- 

 malian eye are present in some form or 

 other. 



Two stages have been studied: (1) At 

 birth, (2) the condition found in the 

 adult. Very little difference is seen in 

 these two stages excepting an increase in 

 size. 



The eye muscles and the optic nerve are 

 easily traced back to the skull. At birth 

 the nerve presents in its course from the 

 eye to the skull a peculiar arrangement. 

 The course is marked by numerous cells 

 and few or no fibers. At the eye there is 

 a rapid change from this cell condition to 

 the fiber condition of the nerve tract. The 

 fibers have not apparently grown much 

 beyond the limits of the eye. In the adult 

 the fibers can be traced to the skull. 



The eye cleft may be seen in cross sec- 

 tions. It is very small and of practically 



the same diameter in both horizontal and 

 vertical sections through it. It meets the 

 eye at such an angle that it is impossible 

 for rays of light, should any enter, to pass 

 through the eye along the axis of vision. 



All the elements of the normal retina 

 are present, but, owing to the much 

 crowded condition, the ganglion cell layer 

 is much increased in thickness. 



The lens, which is found in a great 

 variety of shapes and sizes, is composed 

 of peculiar cartilage-like cells with well- 

 defined nuclei. It is therefore incapable 

 of functioning as a normal lens. 



It is very doubtful therefore whether 

 the eye of the mole functions in any sense. 

 At the best it can do no more than distin- 

 guish between light and darkness. 



The Breeding Habits of Certain Fishes: 

 Jacob Reighard. 



1. Experimental evidence was offered 

 that the nests of Amia are built by the 

 male fish alone. Access to an area of the 

 natural breeding ground was barred by a 

 fyke net, in which fish that attempted to 

 reach the breeding ground were caught 

 and kept living. The males were removed 

 from the net and placed in the natural 

 enclosure behind it; the females were con- 

 fined in a crate. Twenty-three nests were 

 built by the males and of these only five 

 ever contained eggs. These eggs were 

 apparently all laid by one or tM'o females 

 that had gained access to the enclosure. 

 The remaining eighteen nests were never 

 used and were finally abandoned. 



2. It was pointed out that the colors of 

 the male Amia are protective in the breed- 

 ing season. The fins are all colored green 

 in harmony with the surrounding vegeta- 

 tion. The reticulation of the sides is in 

 close imitation of the shadows cast by the 

 interlaced and floating parts of water 

 plants. The tail spot is strikingly like cer- 

 tain refraction images cast on the bottom 



