Further Observations on Koenenia. 413 



Position are entirely covered by the beak wliile they lie in a line 

 almost parallel to the long axis of the animal's bocly. The lateral 

 sensory hairs arise not above bnt on the underside of the carapace 

 which is more curved laterally. Their position is so very near the 

 line of greatest projection that the tips extend from beneath so that 

 they can be seen directly from above. Specimens first examined in 

 this condition, when put in alcohol have a swollen appearance, so 

 that the frontal hairs project upwards. This change is brought aboiU 

 by the elevation of the ventral surface of the beak, on which the 

 Organs are situated, due to a shortening and swelling of the anterior 

 region of the head. The rounding off of the anterior head region 

 and obliteration of the sharp line between the ventral and dorsal 

 surface of the carapace, likewise, elevate the lateral organs tili they 

 appear above the carapace. This slight contraction was noticed in 

 the few perfectly preserved specimens of K. mirahilis which Dr. 

 SiLVESTEi kindly sent me in exchange for specimens of K. ivheeleri. 



III. Yariable aud Fixed Characters. 



From observations on the living Koenenia it is necessary to 

 turn to the results obtained in the examination of many Koenenia, 

 for Information in regard to variable and fixed characters. It seeraed 

 highly probable to me that among animals of Koenenia'^ Position 

 there would be many points of Variation which might be taken for 

 specific characters when only a few specimens were studied, as I 

 had done in considering the various organs of K. ivheeleri. During 

 all my collecting as an active help, likewise in this direction, I was 

 continnally on the lookout for K. parvuJa which was the name I had 

 given to a species, so far represented by a Single specimen, the re- 

 productive appendages and flagellum of which were described by 

 Dr. Wheeler (p. 845). 



By April 12th I had collected about seventy-five specimens, all 

 undoubtedly belonging to the one species. Later collecting, as the 

 above table shows, brought out variations so great in my material, 

 variations that had been given by Hansen as specific characters, 

 that I was at first inclined to think, on superficial examination, that 

 I had not only one but several new species. Abundant material, 

 with more careful examination and comparison soon proved to me 

 ithat I had merely different stages of the one species, Koenenia 

 ^wheeJeril Before describing these three developmental stages it would 

 be best to record very briefly the specific characters of our only 



