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SCIENCE 



[N. S. Vol. XXV. No. 645 



essential agreement with the veins of the 

 same area in modem forms. Such differ- 

 ences as occur are believed to be of less 

 than ordinal value. The order Proto- 

 donata, established by Handlirsch, is not 

 accepted ; the Protodonates being regarded 

 as a suborder of the Odonata. 



Note on the Origin of the Mesoderm of the 

 Poly clad, Planocera inquilina Wh.: 

 Frank M. Surface, University of Penn- 

 sylvania. 



According to Arnold Lang (1884) the 

 mesoderm of the polyclads arises from the 

 whole of the second and third quartets of 

 micromeres. It had been long suspected 

 that Lang was in error, but the subject was 

 not investigated until 1898 when E. B. 

 Wilson published some observations on a 

 species of Leptoplann. He found that all 

 the first three quartets contribute to the 

 formation of ectoderm, while the meso- 

 derm arises by budding in from cells of 

 the second quartet. This mesoderm thus 

 corresponds to the 'larval' mesoderm of 

 annelids and molluscs. Wilson, however, 

 found no evidence of mesoderm arising 

 from members of the fourth quartet and 

 thus in this one important particular the 

 early development of the polyclads dif- 

 fered from the above-mentioned groups. 



In working over the cell lineage of 

 Planocera inquilina it has been definitely 

 determined that in this species, mesoderm 

 arises from the posterior cell of the fourth 

 quartet, i. e., 4d, just aa it does in annelids 

 and molluscs. At the stage of about forty 

 cells, 4d buds into the interior a single 

 large cell which later divides into a right 

 and left moiety from which the mesodermal 

 bands arise. Some of the mesoderm, how- 

 ever, arises from cells of the second quartet 

 as described by Wilson. 



Land Planarians in the United States: L. 

 B. Walton, Kenyon College. 

 Leidy, at a meeting of the Philadelphia 



Academy of Science, August 12, 1851, pre- 

 sented a paper in which he described the 

 first and only species of land planarian 

 (excluding Placocephalus kewensis, an in- 

 troduced form living in hot houses) which 

 has thus far been found in the United 

 States. To this he gave the name Plamaria 

 sylvatica. The five specimens he obtained 

 were collected under flower pots, boxes, 

 etc., in gardens at Philadelphia, and under 

 pieces of bark, and old logs in the woods 

 bordering Wissahicon Creek. On October 

 7 of the same year, after a more critical 

 study of the specimens, he proposed a new 

 genus for their reception, the name thus 

 becoming Rhynchodemus sylvaticus. At a 

 meeting of the society on August 24, 1858, 

 he again referred to the subject stating that 

 since 1851 he had found one specimen in 

 the western part of Pennsylvania on Broad 

 Top Mountain (August, 1857) as well aa 

 several specimens at Newport (July, 1858). 

 Since this time no further observations 

 concerning the collection of additional land 

 planarians in the United States have ap- 

 peared. 



Consequently the occurrence of two dis- 

 tinct species of Rhynchodemus at Gambier, 

 Ohio, is of considerable interest. The 

 first form which may prove identical with 

 the examples procured by Leidy at Phila-. 

 delphia, was found on the partially de- 

 cayed stem of a Virginia creeper, July 9, 

 1904, near Bexley Hall. Five specimens 

 were obtained, while additional representa- 

 tives have been found at the same place 

 each succeeding sununer. During Novem- 

 ber of the past year a single specimen was 

 also taken under a stone in a meadow, 

 some three miles south of the preceding 

 locality. The specimens mentioned agree 

 closely with the description given by Leidy 

 as well as with his drawing of the Phila- 

 delphia forms published in Girard's paper 

 on planarians {Ann. sc. Nat. Zool., 7 ser., 

 pp. 145-310, 1894). The length is greater 



