215] REGENERATION OF CRAYFISH APPENDAGES 27 



It is noticeable that there is no such well-defined row of cells 

 along the sides beneath the old cuticle (o. c). At each side and 

 above the distal segment of the optic ganglion, is a very con- 

 spicuous, loose network of connective-tissue fibres (cc.) which 

 is the characteristic tissue formed in the regenerating eye. At 

 each side are bands of muscle (m.) belonging to the eye-stalk. 

 In the upper right-hand portion of the figure are shown several 

 small masses of pigment granules, which have no definite size, 

 shape or arrangement and are probably a part of the pigment of 

 the old retina that had not been entirely removed. Although 

 undoubtedly new tissue has been formed, there is nothing to in- 

 dicate that a functional eye is being regenerated. 



In Fig. 22 is seen a regenerating eye that is even more ab- 

 normal in shape than the one shown in the preceding figure. 

 Here the irregularity of outline is not due to unequal develop- 

 ment of the cuticle, but of the tissues beneath the cuticle. The 

 regenerated portion of the cuticle extends from a to b and pre- 

 sents, instead of a smooth convex outline, a very much convo- 

 luted one. Even the lower, old portion of the eye appears to 

 have suffered considerable distortion. In the depression at d 

 and around the outer surface of the new cuticle is a granular 

 aggregation which probably is partly a mucous secretion from 

 the glands beneath the cuticle, and partly degeneration products, 

 together with an admixture of bacteria. At ba there are numer- 

 ous small, ill-defined bodies which can only be interpreted as be- 

 ing a bacterial zoogloea. In this section the hypodermis forms 

 a continuous layer beneath both old and new portions of the 

 cuticle. Besides the optic nerve (op.) and ganglion (gl.) very 

 little internal structure is to be seen, except the loose connective 

 tissue network. To the right at m, are some small muscle bands 

 and just internal to these is a well defined connective tissue band. 

 As in the preceding figure, there is nothing to indicate that the 

 ommatidia are being: regenerated. 



