730 



SCIENCE 



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



exist in any fin, unpaired as well as paired. 

 The pectoral g-irdle is proved to be not 

 serially homologous with the gill arches. 

 In Heterodontus the pectoral girdle is 

 shifted forward during development to- 

 ward the gill region instead of away from 

 it as the gill-areh theory assumes. THe 

 attachment of the trapezius muscle, as- 

 sumed by the adherents of the gill-arch 

 theory to be 'an old relic of a former 

 branchial musculature supplying the shoul- 

 der girdle,' is shown instead to be sec- 

 ondary. The pelvic arch has primarily no 

 dorsal prominence homologous with the 

 scapular portion of the pectoral arch, but, 

 on the other baud, the pectoral arch passes 

 through a stage similar to the pelvic arch 

 when only the ventral portion is present. 

 Hence neither of them is to be regarded 

 as a modified gill arch. In all fins the 

 condensation or thickening of the mesen- 

 chyme, from which the skeleton is later dif- 

 ferentiated, begins always in the fin-fold in 

 contact with the ectoderm and extends in- 

 ward, and is thus of external origin in 

 contrast to that of the gill arches which 

 arises next to the endoderm of the pharynx. 

 In the paired and unpaired fins the 

 sequence of development of the various 

 structures is identical. The above facts 

 show such striking similarity between the 

 paired and unpaired fins, in the develop- 

 ment of all structures, and such contrast 

 with the gills, as to strongly support the 

 fin-fold theory of Thacher, Balfour and 

 Mivart. 



On the Structure, Development and Rela- 

 tionship of Blastoidocrinus {Billings 

 1859) : Geoege H. Hudson, Plattsburgh, 

 Clinton Co., N. Y. 



The only known species of the genus was 

 described by Billings in Cam. Org. Rem., 

 Decade IV. (1859). F. A. Bather in 

 Part III. of the 'Treatise on Zoology' 



edited by B. Ray Lancaster gives it a 

 family of its own and has placed it with 

 Asterohlastus under Grade A, Proto- 

 Uastoidea Bather (1899). The elaborate 

 hydrosphere folds would cut it out of this 

 grade, however, and while it has an ambu- 

 lacral system like that of the Edrioaster- 

 oidea its brachioles would alone exclude it 

 from that class. The present paper is 

 based on a very perfect specimen (frag- 

 ments only have been heretofore known), 

 and on fragments and some thousand single 

 and very perfect plates from specimens of 

 different ages. The paper presents new 

 and remarkable elements in Echinoderm 

 structure, some from internal structures 

 displayed by a section from the perfect 

 specimen, and the development of many 

 structures from five areas of 'primary 

 meristem,' one each at the distal ends of 

 the rays. Cystid, blastoid edrioasteroid 

 and crinoid characters were briefly men- 

 tioned. The form has been made the type 

 of a new order Parablastoidea. A more 

 complete description is published in N. Y. 

 State Museum Bulletin 107, p. 97. 



Notes on the Periodical Literature of the 

 Smaller Domesticated Animals: C. B. 

 Davenport, Cold Spring Harbor, N. Y. 

 There is a mass of current periodical 

 literature on the domesticated animals 

 that is not taken cognizance of in the 

 zoological bibliographies nor in those of 

 agriculture. Consequently they are un- 

 known to most zoologists. With the 

 revival of scientific interest in breeding 

 this literature becomes of great importance 

 because it tells where stock is to be obtained 

 and because it contains suggestive data on 

 the factors of evolution. Taken together 

 this mass of periodical literature consti- 

 tutes a history of the current evolution of 

 domesticated animals of the most detailed 

 and intensive sort. 



