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9. Later the lens, and especially the vitreous body, degenerated more 
rapidly than the retina. 
10. The eye of Typhlichthys has degenerated along a different line from 
that of Amblyopsis, its pigmented epithelium haying been most profoundly 
affected. 
11. The eye muscles have disappeared in Typhlichthys. 
12. Troglichthys shows that the steps in the degeneration of the muscles 
were in the direction of lengthening their attaching tendons, finally replacing the 
muscles with strands of connective fibres. 
13. The scleral cartilages have not kept pace in their degeneration with the 
active structures of the eye. 
14. The lens in the blind species is, for the most part, a small group of cells 
without fibres. 
15. The proportional degeneration of the layers of the retina is shown in 
diagram j. 
16. With advancing age the eye of Amblyopsis undergoes a distinct onto- 
genic degeneration from the mature structure. _ 
17. The phyletic degeneration does not follow the reverse order of develop- 
ment. None of the adult degenerate eyes resemble stages of past (phyletic) adult 
conditions. 
18. The degenerate eyes do not owe their structure to a cessation of develop- 
ment at any past ontogenic stage, i. e., at any stage passed through in the de- 
velopment of a normal life. 
19. Cessation in development occurs only in the reduction of the number of 
cell generations produced to form the eye not in cessation of morphogenic pro- 
cesses. 
20. In some cases (Typhlichthys) there is a retardation in the rate of de- 
velopment, the permanent condition being reached later in life than is usual in 
fishes. (It is possible that the pigment of the pigment epithelium never comes 
to develop at all. It is, however, impossible to assert this until the embryos of 
this species are examined. It is possible that the pigment degenerates before the 
stages are reached that I have examined. ) 
21. The degenerate condition of the eye appears in theembryo. The crowd- 
ing back has followed the law of tachygenesis. 
22. The conditions in the eyes of the Amblyopside can only be explained 
as the result of the transmission of disuse effect. 
16—SCIENCE. 
