Regeneration in Compound Eyes of Crustacea 203 



been removed. In no case is there any evidence that the optic 

 ganghon regenerates. Consequently this difference would remain 

 unchanged. 



B CASES OF ABERRANT REGENERATION OF OMMATIDIA 



In study of the regenerating eye several cases of aberrant regen- 

 eration of ommatidia have come under observation. One case 

 deserves especial mention. Fig. 36, a and h represent ventral sur- 

 face views of an injured right eye and the normal left eye of a 

 Palaemonetes. Judging both from the surface indications and an 

 examination of the sections the right eye must have been cut off 

 at a level corresponding approximately with the line a-h shown 

 in the figure of the normal eye. A cut at this level would remove 

 the upper two sections of the optic ganglion and injure the third. 

 It would also cut across the heavy muscle band lying in the 

 posterior part of the eye stalk. 



The experiment covered thirty days, one moult taking place 

 ten days after the operation. Casual surface examination was 

 sufficient to show that a rather large amount of new tissue had 

 formed and that a spot of pigment had developed on the- ventral 

 side of the stump. The growth of such a large amount of new 

 tissue is quite unusual when so much of the ganglion has been 

 removed. 



A study of the sections gives additional information regarding 

 this new tissue. In Fig. 56 the tissue lying between the periphery 

 and the broken line extending from x to y represents approxi- 

 mately the amount of new tissue. Careful examination shows 

 a difference in the character of the differentiacion of the regener- 

 ated tissues in the different regions. This figure is from a section 

 so near the dorsal surface that but httle of the nerve tissue appears. 

 Near the right side of the figure a conspicuous section of the old 

 muscle band is seen. Just distal to the muscle band the new tissue 

 is more dense and compact than in the remaining part of the 

 regenerating tissue. This band of new tissue {nt) is composed of 

 fibers extending inward from the periphery and joining end to end 

 with the fibers of the old muscle band, thereby forming a contin- 



