496 



SCIENCE 



[N. S. Vol. XXXIV. No. 876 



elude using this method as a regular routine 

 analysis for all soils. 



There are several reasons explaining the 

 divergence of these factors from the average. 

 To obtain one factor which would obtain for 

 all soils, the silt particles (and likewise the 

 clay) would have to be of a uniform size, 

 shape and weight. These conditions do not 

 exist in nature. However, if one size graded 

 into the next, and the shape and specific grav- 

 ity of the material were fairly uniform, the 

 factors would still not be widely divergent. 

 Another difficulty enters here; not only is this 

 hypothesis doubtful, but it is not possible, on 

 account of the great difference in size of the 

 largest silt particles and the smallest clay 

 particles, to have a counting plate and ob- 

 jective so calibrated that the very small clay 

 particles could be counted and at the same 

 time to give a field large enough to include a 

 number of silt particles. So in order to get 

 the silt it was necessary to use a low-power 

 objective, and consequently many of the 

 smaller clay particles were not counted. 



The disadvantages of the method are that 

 it is not applicable in every instance because 

 of the small mass of clay particles in some 

 soils; that the counts are not sufiiciently uni- 

 form where great accuracy is necessary; and 

 that in order to get the best results the opera- 

 tor must have a large experience in the usual 

 methods of analysis. 



C. C. Fletcher 



Bureau of Soils, 

 Washington, D. C. 



on a posterior communication op the air- 

 bladder with the exterior in fishes 

 Recently, while examining the visceral 

 anatomy of Ophiocephalus, my attention was 

 called to what appeared to be a posterior com- 

 munication of the air-bladder with the ex- 

 terior. My species is Ophiocephalus macu- 

 latus, and before its death had been an aqua- 

 rium pet of a Chinese in Redwood, California. 

 Hence from whence it came is not known, but 

 doubtless from somewhere in China, for many 

 of this singularly hardy fish are carried alive 

 by the Chinese from their home country. 



The abdominal cavity of Ophiocephalus ex- 

 tends for a greater distance behind the anal 

 opening than in front of it for the accommo- 

 dation of the very long air-bladder, which 

 reaches almost to the base of the caudal fin. 

 About midway in the length of the air-bladder 

 a wide tube of thin membrane is attached, 

 which opening at its lower end to the exterior 

 through the genital pore, appears at first sight 

 to be a duct from the air-bladder, more espe- 

 cially as it is of the same white, glistening 

 membrane. It, however, ends blindly against 

 the wall of the air-bladder where it is so firmly 

 attached by the incasing fibers of the latter 

 extending over and around it that considerable 

 tearing is necessary to detach it. Both the 

 tube and the air-bladder, where the tube joins, 

 were opened and examined under the micro- 

 scope but no opening was found in either. 

 The end of the tube is round and blunt. Into 

 its lower end the vas deferens opens. Just 

 above where the vas deferens enters, or just 

 below the middle of its length, the tube ex- 

 pands into a large triangular pocket with a 

 blunt point directed forward. 



Almost a century ago Weber (" De aure et 

 audita Hominis et animalium," Leipzig, 1820, 

 p. Y3) described in Clupea harangus a com- 

 munication from the posterior end of the air- 

 bladder with the exterior through a duct open- 

 ing with the vas deferens into the genital pore. 

 This condition being so nearly parallel with 

 that described above for Ophiocephalus leads 

 me to question whether the tube described by 

 "Weber was not also a blind tube, and not 

 actually opening into the air-bladder. 



Having no specimens of Clupea harangus, 

 and having other problems on hand, I have 

 not attempted to go more deeply into this 

 subject. As the supposed fact that Clupea 

 harangus has a posterior opening to the air- 

 bladder has been repeated several times since 

 the time of Weber without any one attempting 

 to verify his work (or at least indicating that 

 he has verified it), it is desirable that some 

 one do so. I pass the problem on for what it 

 may be worth. 



Edwin Chapin Starks 



