784 



SCIENCE. 



[N. S. Vol. VII. No. 179. 



the tension in the ring of P,N,OnH,^ is too great 

 to permit of its existence and it spontaneously 

 takes up water, forming PiNjOijHie. A further 

 confirmation is found in the fact that the higher 

 members on decomposition in part close again 

 to form the stable ring-acid P^N^OgHe, indica- 

 ting a disposition to form rings containing P4N^. 

 An attempt to test this theory further will be 

 made by endeavoring to prepare diphosphoni- 

 trilic chlorid, P.N^Clj. The corresponding 

 meta-phosphimic acid, PjNoOjHj, should have 

 the angle 90°, differing from the angle of least 

 tension, 135°, by 4.5°. Such an acid should be 

 much less stable than even PvN.Oj^Hy and 

 should pass at once into P2N.2O5H5. 



William H. Kbug, 



Secretary. 



ACADEMY OF NATURAL SCIENCES OF PHILADEL- 

 PHIA, MAY 17. 



Mr. C. S. Boyer illustrated the structure and 

 geographical distribution of diatoms by a large 

 series of lantern views preparatory to describ- 

 ing the following new species: Rhabdonema Wool- 

 manianum, Biddulpliia semicircularis Asburyana, 

 B. argus, B. interrupta, B. keeleyi, B. Shulzei and 

 B. verrucosa. The paper, with figures, will be 

 published in the Proceedings of the Academy. 



Mr. T. C. Palmer described and illustrated 

 some of the phenomena of conjugation in Clos- 

 terium. The essential steps are essentially as 

 in Spirogyra, in that in both cases the process is 

 at first a putting out of tubes which meet and 

 fuse. But just as Closterium differs from Spiro- 

 gyra in its method of cell-division, so it presents 

 peculiarities in manner of formation of the 

 zygospore. The two lobes of the desmid seem 

 to possess a certain degree of individuality, at 

 least at the period of conjugation. These lobes, 

 owing to the peculiar method of growth of the 

 plant, generally differ, at the time of conjuga- 

 tion, in age, and therefore in size, and in the 

 thickness, color and markings of the cell-walls. 

 The contrast between two ends or lobes of a 

 given cell is often very great ; and in C. acero- 

 sum, as a rule, each desmid first separates into 

 two entirely distinct and independent semi-cells, 

 each of which is beautifully rounded off at its 

 blunt end by a new growth of cell-wall. The 

 young semi-cell of each desmid then conjugates 



with the old semi- cell of the other, and two 

 perfectly distinct zygospores are thus formed. 

 These zygospores and the empty semi-cell cases 

 are held together by a nearly or quite invisible 

 jelly. The ' individuality of the semi-cell,' a 

 tendency toward which has been remarked 

 upon heretofore by Mr. Archer in the case of 

 C. lineatum, here becomes practically complete. 



In one instance C. aeerosum formed three 

 zygospores instead of two. One of these was 

 the usual size, made up of the commingled con- 

 tents of an old and new semi-cell. The other 

 two were about half the size, and consisted each 

 of the unmixed contents of another semi-cell. 

 Of a similar nature is the recently observed 

 discharge, without conjugation,. of the contents 

 of a whole cell in C. lineatum. The protoplasm, 

 containing small round or ovoid bodies like 

 those in the ordinary zygospore, issued from 

 the ruptured union of the semi-cell cases. It 

 assumed a spherical form. Its development 

 could not be followed further. 



The development of the zygospores of Clos- 

 terium is not thoroughly well understood, but 

 the phenomena are probably similar to those of 

 the germination of Cosmarium. In addition, 

 however, to this process, another method of 

 reproduction is suspected in Closterium, of which 

 the discharge of the cell-contents without con- 

 jugation may be one of the stages. 



Many of the phases of reproduction in the 

 desmids may be observed to advantage by plac- 

 ing zygospores in life-slides and following 

 the changes that ensue. In such slides large 

 numbers of very minute Closterium frequently 

 appear, and these grow perceptibly from day 

 to day, but it is not certain, or even probable, 

 that these arise from the ordinary zygospore. 



The following papers were presented for pub- 

 lication in the Proceedings : 



' Descriptions of five new Phyllostome Bats,' 

 by Gerrit S. Miller, Jr. 



' Chitons collected by Dr. Harold Heath at 

 Pacific Grove, near Monterey, Cal.,' by H. A. 

 Pilsbry. Edward J. Nolan, 



Recording Secretary. 



Erratum : In the review of Wilder's System of 

 Nomenclature, p. 716, col. 1, line 5, for 'chippo- 

 camp' read 'hippocamp.' 



