March 9, 1883.] 



SCIENCE. 



149 



lamellae closely placed, and crossed at right angles by 

 others apparently superimposed and of the same na- 

 ture. He has been able, by separating the layers 

 composing the thallus, to see that these bands anas- 

 tomosed at their points of conjunction, leaving be- 

 tween them empty spaces of the same width as the 

 bands, composing a kind of latticed thallus like that 

 of species of Agarum. — ( Comptes retidus. June 26. ) 

 L. L. [330 



Permian plants from eastern Russia. — After 

 giving a vertical section of the upper Permian of 

 Kargalinsk, Twelvetrees describes a Cardiopteris, two 

 species of Walchia, one Lepidodendron, one Scliizo- 

 dendron, one Anomorrhoea, a Caulopte™ (?), and 

 four Calamites. These plants have, taken altogether, 

 a remarkable analogy with a group of vegetable 

 remains procured from strata near Fairplay, Col., 

 and which, by their characters, are of lower Permian 

 age. The affinity is rendered the more remarkable 

 by the fact, that, as remarked by the English author, 

 "The list of the species of plants has a i^aleozoic 

 aspect, but a secondary one as respects the reptilian 

 remains." The same can be said of fossil remains 

 of Fairplay, the plants being all of paleozoic types; 

 while the insects, according to the i-esearches of Mr. 

 Scudder, are mesozoic. — {Quart, journ. (jeol. sar. 

 Land., no. 152.) L. L. [331 



ZOOLOGY. 



( Geograp/iici^l disiribuiion.) 

 The relations of the ' nearctic ' region. — A 



re-examination of Wallace's palaearctic and nearctic 

 regions is being made by A. Heilprin. 



Two propositions are discussed: namely, 1°, whether 

 the nearctic region is entitled to independent rank; 

 and, 2°, if not, to which of the two regions, neotrop- 

 ical or palaearctic, does it belong. For the mammals, 

 Wallace's tables are recast. It is shown, tliat, while 

 eighteen neotropical and nineteen palaearctic families 

 occur in the nearctic region, only eleven genera are 

 common to the nearctic and neotropical regions, as 

 opposed to twenty-one genera common to the latter 

 region and the palaearctic. The number of genera 

 peculiar to the nearctic region amounts to 35 per cent; 

 to the palaearctic, 35 per cent; to the oriental, 46 per 

 cent; to the Australian, 64 per cent; to the Ethiopian, 

 63 per cent; and to the neotropical, 78 per cent. The 

 number of families peculiar to the nearctic is given as 

 one; to the palaearctic, none; while all the remaining 

 regions have from seven to nine. By uniting the first 

 two regions, the proportion of peculiar genera is raised 

 to fifty per cent, and the number of peculiar families, 

 including Rogiferidae, Alcadae, and Copridae (though 

 without warrant in this case, as it appears to us), to 

 seven, thus bringing the combined regions into rank 

 with remaining divisions of the globe. In conclusion, 

 it is considered proved: "first, that by family, ge- 

 neric, and specific characters, as far as mammals are 

 concerned, the nearctic and palaearctic faunas taken 

 collectively are more clearly defined from any or all 

 tlie other regions than either the nearctic or palae- 

 arctic taken individually; and, second, that by the 

 community of family, generic, and specific chai'ac- 

 ters, tlie nearctic region is indisputably united to the 

 palaearctic, of which it forms a lateral extension." 



It would appear that the first conclusion does not 

 entirely satisfy the first proposition, and that the 

 second conclusion should be reversed; since, accord- 

 ing to the percentages given, the palaearctic region 

 is the lateral extension of the nearctic. Among the 

 many thoughts to which the paper (which is not yet 

 completed) gives birth, the following maybe recorded : 



1°. Even after combining the two nortliern regions, 

 the interval between their percentage of peculiar 

 genera and that of the region having the next higher 

 number is greater than that between percentage of 

 the palaearctic region alone and that of the region 

 having the ne.Kt higher number. 2°. The number of 

 families peculiar to the combined regions, according 

 to Wallace's tables (excluding the ungulate sub- 

 families), is but one more than the number of families 

 peculiar to the nearctic region alone according ia 

 Allen's tables. 3°. The character of the peculiar 

 families inhabiting the Australian region is very dif- 

 ferent from that of those of the other regions, since 

 in tlie former case six of the eight families belong ta 

 one order, while in the latter the families are divided 

 among the many orders of Monodelphia. 4°. A. 

 knowledge of what regions are occupied by a group 

 of animals is of more importance to the zoologist 

 than the knowledge of what animals occupy any 

 region or regions ; especially if, in the latter case, no 

 account is taken of extinct forms. — (Proc. acad. nat. 

 sc.PAitacZ., 1882, 316.) P. w. T. [332 



{General physiology and embryology.) 



Action of digitaline on the circulatory organs 

 (lireliminary note by H. H. Donaldson and L. T. 

 Stevens). — The continuation of the experiments 

 begun last year has yielded the following results : the 

 work done by the heart of the common frog is de- 

 creased by digitaline, whatever the dose, as was 

 previously shown to be the case for the heart of the 

 ' slider ' terrapin. In both frog and terrapin, the 

 decrease occurs, whether the aortic valves are intact 

 or not. Variations in arterial or venous pressure do 

 not affect the result. 



By a method permitting direct measurement of the 

 fluid circulating through the viscera and lower ex- 

 tremities in a unit of, time and under constant press- 

 ure, it has been determined for the frog that the 

 arterioles are constricted by digitaline. On this point 

 the terrapin has not yet been investigated. Digita- 

 line has also been shown to increase mean blood 

 pressure in both frog and terrapin. 



We have, then, for the frog under digitaline a de- 

 crease in the work done by the heart, a rise of mean 

 blood pressure, and a constriction of the arterioles. 

 The first and second of these points have been already 

 demonstrated for the terrapin as well. — {Johns Hopk. 

 univ. circ, Feb., 1883.) [333 



Origin of the heart. — Professor Biitsclili has ad- 

 vanced a hypothesis of the phylogenetic origin of the 

 heart and blood-vessels, which has much plausibility. 

 He suggests that the heart is a remnant of the primi- 

 tive or segmentation cavity of the embryo, and is not 

 derived from the secondary or permanent body cavity 

 (schizocoele or enterocoele). He endeavors to recon- 

 cile this view with the accounts of the develoi^ment 

 of the heart in vertebrates, maintaining that it proba- 

 bly arises as a fissure in the mesoderm, remaining as 

 a permanent part from the temporary primitive cav- 

 ity. More support for the hypothesis is found in 

 arthropods; for it has been observed in several forms 

 that the two edges of the mesoderm approach one 

 another in the median dorsal line, leaving a space 

 between them, which belongs to the primitive cavity. 

 This space becomes the heart. Sometimes it is cut 

 off before, sometimes after, the mesoderm is split into 

 segments. These observations were upon the bee 

 (Biitsclih), Geophilus (Metschnikoff), and Branchipus 

 (Clans). An investigation to answer the problem 

 propounded by Biitschli would, it may be safely said, 

 prove fruitftfl and interesting. — {Morph. jahrbuch, 

 viii. 474.) c. s. m. [33* 



