Rec^cfuration in Compound Eyes of Crustacea 229 



Large blood sinuses are present in the heteromorphic append- 

 ages. Aside from these no tissues are apparent except the hypo- 

 dermis and the fibrous sheath which encloses the nerve bundles 

 and the nerves themselves. In some instances muscles are found 

 in the base of the appendage but these are probably remains of the 

 base of the eye stump. 



Material has been insufficient to make detailed observations 

 upon the character of the masses of sensory cells found m the 

 ganglion-Uke groups throughout the appendage. Sufficient obser- 

 vations have been made, however, to warrant the conclusion that 

 they are concerned with the innervation of the hollow sensory 

 hairs. In a few instances processes have been traced into the 

 bases of the hairs which open by a wide mouth into the interior of 

 the appendage (Figs. 78 and 79). 



Herbst has considered the microscopic structure of these hetero- 

 morphic appendages in considerable detail and has examined a 

 number of different stages. He describes the nerve cells as 

 grouped into spindle-shaped ganglia with groups of nerve fibers 

 extending from each end of the spindle-shaped masses, the distal 

 bundle of strands being connected with the sensory hairs while the 

 proximal bundle passes inward toward the brain. None of the 

 stages examined by Herbst were younger than about six months, 

 however, and consequently any structures that had developed 

 would likely be much more definitely organized than in the 

 appendages examined in this series of experiments. 



Herbst considers that these ganglion-like groups of cells have 

 developed from the hypodermis and that in the earlier stages they 

 have no direct connection with the brain. In later stages, how- 

 ever, he describes the proximal bundles of the several ganglia as 

 uniting to pass inward to the brain. But in most cases at least he 

 considers that there is no union with the old optic nerve and con- 

 sequently that the connection of the appendage with the brain is 

 secondary. He mentions the similarity between these epithelial 

 sense cells and those found in the first antenna, homologizing the 

 sensory hairs which are found on the appendage with the olfactory 

 set^ found upon the first antenna. Finally he comes to the con- 

 clusion that both in form and structure the heteromorphic append- 



