412 NATHAN FASTEN. 



4. In size, the median ocellus is about two thirds the dimen- 

 sions of either of the lateral ones. 



5. Each ocellus is constructed somewhat similarly. It is em- 

 bedded in a semi-lunar cup whose internal surface is thickened 

 into a basal plate. Covering the external face of the ocellus is 

 a cuticle which is divided up into squares that appear like the 

 facets of ommatidia. 



6. Interiorly every ocellus contains numerous retinal cells. 

 There are nine of these cells in each lateral ocellus and five 

 of them in the median ocellus. 



7. The retinal cell possesses a large, rounded nucleus and a 

 single rod-like, heavily staining phaosome, which is located 

 between the nucleus and the basal plate. 



8. The optic nerve which makes its way from the ocelli to 

 the brain consists, in all probability, of twenty-three nerves 

 corresponding to the number of retinal cells found in the eye. 



BIBLIOGRAPHY. 

 Esterly, C. O. 



'08 The Light Recipient Organs of the Copepod Eucalanus elongatus. Bui. 



Mus. Comp. Zool. Harvard College, Vol. 53, No. i, pp. 3-56. 

 Fasten, N. 



'12 The Brook Trout Disease at Wild Rose and Other Hatcheries. (The 

 Brook Trout Disease in Wisconsin Waters.) Rep't Wis. Fish Com., 1911- 

 1912, pp. 12-22. 

 '13 The Behavior of a Parasitic Copepod, Lernaeopoda edwardsii Olsson. 



Jour, of An. Beh., Vol. 3, pp. 36-60. 

 '14 Fertilization in the Parasitic Copepod, Lernaeopoda edwardsii Olsson. 



BIOL. BUL., Vol. 27, No. 2, pp. 115-127. 

 Wilson, C. B. 



'n North American Parasitic Copepods. Part 9. The Lernaeopodidae. 



Proc. U. S. Nat. Mus., Vol. 39, pp. 189-226. 



'15 North American Parasitic Copepods Belonging to the Lernaeopodidae, with 

 a Revision of the Entire Family. Proc. U. S. Nat. Mus., Vol. 47, pp. 565- 

 729. 



