April 6, 1906.] 



SCIENCE. 



527 



The Regeneration of an Antenna-like Or- 

 gan in place of the Vestigial Eye of the 

 Blind Crayfish: Charles Zeleny, Uni- 

 versity of Indiana. 



In the blind erayfisli {Cambarus pel- 

 lucidus testii) the eyes have become degen- 

 erated to such an extent as to be perfectly 

 functionless. The retinal structures if 

 present at all are represented merely by a 

 few small groups of granular cells. The 

 right eye-stalk was removed in nine speci- 

 mens of this crayfish. Three lived for a 

 year after the operation. One of these 

 regenerated an antenna-like organ in place 

 of the removed eye-stalk. The new organ 

 is segmented and the terminal half is cov- 

 ered with tactile hairs. All appearances 

 point toward the supposition that the organ 

 is a functional one and its function is prob- 

 ably tactile in character. The instance, 

 therefore, represents a case of the regen- 

 eration of a functional organ to replace a 

 removed non-functional one. 



The Young of Scutigerella immacxdata: 



S. R. Williams, Miami University. 



A Scutigerella, which had remained 

 quiescent for ten days beneath a glass 

 slide (in a bubble of air) in a stender dish, 

 laid eight eggs on May 25, 1904. 



She remained with the eggs continuously 

 until they hatched on June 6. June 7 

 one was removed. It proved to have six 

 pairs of legs, as was previously stated to be 

 the probability at the St. Louis meeting of 

 the Association for the Advancement of 

 Science. 



The disturbance of the nest caused the 

 mother to desert the remaining young and 

 by the morning of the following day these 

 had all disappeared. It is practically cer- 

 tain that they were eaten by the other 

 Scutigerellas in the stender dish. 



The San Diego Marine Biological Associa- 

 tion and its Work: C. C. Nutting, Uni- 

 versity of Iowa. 



Some Points on the Haiits and Anatomy of 

 Placobdella Pediculata, N. Sp.: Henry 

 P. Nachtrieb, University of Minnesota. 



Aw Ecological Survey of Isle Royal, Lake 

 Superior: Chas. G. Adams, University of 

 Michigan. 



The Pearl Organs and Spawning Behavior 

 of American Suckers and Minnows and 

 their Bearing upon Current Theories of 

 the Origin of Secondary Sexual Charac- 

 ters: J. Reighard, University of Michi- 

 gan. 

 Some Relations of Protozoa to Certain 

 Ions in their Medium: A. "W. Peters 

 and M. H. Rees, University of Illinois. 

 In one series of experiments the resist- 

 ance of Paramcecia to low concentrations 

 of H and OH ions was tested by keeping 

 the animals in media consisting of pure 

 salt solutions made to contain a serial range 

 of known concentrations of H and OH ions. 

 Tests were also made with distilled water. 

 No food or other organic matter was pres- 

 ent in any of these media. The numerical 

 results showed a greater resistance in the 

 OH than in the H media. In another 

 series of experiments further tests upon 

 the resistance of Paramcecium and Colpid- 

 ium to H and OH ions were made under 

 conditions as nearly natural as possible. 

 The original nutritive media were sub- 

 jected to quantitative chemical and phys- 

 ical examination and in different portions 

 of these media a serial range of concentra- 

 tions in H and OH was produced and also 

 quantitativelj' estimated. The animals 

 having lived for twenty-four hours or 

 longer in media so prepared, were sub- 

 jected in the same media to instantaneous 

 killing tests, one of which consisted of pure 

 HCl, the other of HCl -f- NaCl. The least 

 gram ionic concentration of H which killed 

 instantly was accurately determined and 

 was taken as the measure of resistance. 

 Curves representing all the results show 



