Febbuaet 17, 1911] 



SCIENCE 



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whereby the various zoological organizations of 

 America can unite in an eifort to influence the 

 International Commission on Nomenclature in the 

 direction of securing greater flexibility in the 

 interpretation of its own rules. The committee 

 was given power to perpetuate itself. 



The chair was authorized to appoint a com- 

 mittee whose function it shall be to recommend 

 to the society plans for an agreement between its 

 members regarding the form and manner of pre- 

 senting papers for publication. Such plans shall 

 have for their purpose the aiding of other investi- 

 gators in arriving at an understanding of the 

 methods and conclusions of writers with the least 

 possible expenditure of time and efi'ort. 



Officers for the ensuing year were chosen as 

 follows : 



President — George Lefevre, University of Mis- 

 souri. 



Vioe-president — E. H. Waleott, University of 

 Nebraska. 



Secretary-Treasurer — H. V. Neal, Knox College. 



Executive Committee — H. B. Ward, University 

 of Illinois (for three years) ; Chancey Juday, 

 University of Wisconsin; H. W. Norris, Grinnell 

 College. 



The following, having received the votes of a 

 majority of the executive committees of both 

 branches, were elected to membership in the 

 Central Branch: Dr. G. W. Tannreuther, Univer- 

 sity of Missouri; Dr. A. G. Ruthven, University 

 of Michigan; Dr. R. C. Mullenix, Yankton Col- 

 lege; Mr. H. Walton Clark, Bureau of Fisheries, 

 Fairport, Iowa. 



The following are titles and abstracts of papers 

 presented at the meeting: 

 Organ Inversion in Trematodes: F. D. Baekeb, 



University of Nebraska. 



Situs inversus viscerum in varying degrees has 

 long been known to occur in man. This deviation 

 from the normal position of organs also occurs in 

 a number of animals such as the tadpoles, flat- 

 fishes and molluscs. Variation in the position of 

 the genital organs or sexual amphitypie is very 

 common in the trematodes. From the examina- 

 tion of original specimens and the literature I 

 have found this variation occurs in at least 26 

 different species, embracing 11 different genera 

 of distomes and one genus of monostomes. The 

 percentage of sexual amphitypie varies from 3 

 per cent, in some species to 50 per cent, in others. 

 The degree of transposition of organs varies from 

 the transposition of a single organ to that of six 

 organs, in many cases other organs than the 



sexual organs are transposed, in which cases the 

 term situs inversus is more applicable. Where 

 only one or two organs are transposed this should 

 be designated as partial sexual amphitypie. 



A number of theories as to the cause of situs 

 in/versus has been advanced, among which are 

 " the preponderance of the omphalo-mesenteric 

 vein," " the persistence of the left venous trunks," 

 " discontinuous substantive variation," " a condi- 

 tion essential to the existence of the organism," 

 " inversion through sympathy." 



Experimental work on incompletely separated 

 blastomeres of the frog, sea-urchin, mollusc, etc., 

 shows that such blastomeres give rise to twin 

 embryos, one of which is a " mirror image " of 

 the other. This suggests the possibility that 

 " mirror images " or sexual amphitypie in the 

 trematodes may be due to the development of 

 twin trematodes which have arisen from com- 

 pletely separated portions of the " germ balls " 

 in the sporocyst or redia stages. 



Fuller account to be published later; place 

 undetermined. 

 Gametogenesis in Tcenia serrata: R. T. Young, 



University of North Dakota. 



Testes and ovaries arise from undifferentiated 

 parenchyma cells. Oogonia and spermatogonia 

 are similar in structure and appear to arise sim- 

 ilarly. No mitoses are found in the early stages 

 of development of these cells. Amitoses, while 

 present, are too infrequent to account for the 

 multiplication of the primitive sex cells, and it 

 is probable, although not certainly demonstrable 

 as yet, that increase is partly due to the develop- 

 ment of nuclei either de novo or from chromidial 

 extrusions from preexistent nuclei. 



The spermatocytes of the first order arise from 

 the spermatogonia by an enlargement of the 

 nucleus and the formation of a skein from its 

 reticulum. The spermatocytes fuse to form cyto- 

 phores with subsequent breaking up of the skeins 

 and commingling of the skein remnants with the 

 cytoplasm of the latter. The secondary sperma- 

 tocytes arise in the cytophores either de novo or 

 from the skein remnants of the first spermato- 

 cytes. The spermatozoa are formed directly from 

 the cytoplasm of the cytophores. In oogenesis 

 skeins are similarly formed subsequent to the 

 growth period and similarly degenerate without 

 the occurrence of later stages of mitosis at this 

 time. As the ova are leaving the ovaries or after 

 reaching the uterus an abortive maturation 

 mitosis occurs, without however the appearance 

 of polar bodies; the cell or cells which have been 



