582 SUMMARY OF CURRENT RESEARCHES RELATING TO 



regard distinguishes two groups — (1) those in whicli a seminal reservoir 

 and accessory gland are present ; (2) those in which the accessory gland 

 is absent, and the seminal reservoir approximated to the orifice of the oviduct. 

 The female genital armature formed from the ninth urite is then discussed, 

 with special reference to the conclusions of Lacaze-Duthiers. The histo- 

 logical details of M. Beauregard's careful investigations are hardly adapted 

 for compressed summary. 



Fossil Insects.* — Dr. S. H. Scudder gives a systematic review of our 

 present knowledge of fossil insects, including myriopods and spiders. It 

 is essentially a translation for the benefit of English readers of the text 

 furnished by the author to Dr. Zittel for his ' Handbuch der Paleontologie.' 

 The German text, however, is accompanied by more than two hundred 

 illustrations. M. Barrois is also publishing a French version. Each 

 section of the vpork is accompanied by a complete bibliography, vv^hich 

 shows at a glance how recently this department of paleontology has been 

 developed (very few of the titles dating back beyond 1850), and how 

 extensive and varied the author's own contributions have been. The con- 

 cise descriptions of the classes, orders, and families are accompanied by 

 brief notes on the fossil genera and species, with the locality and geological 

 horizon in many cases ; while the stratigraphic distribution and range of 

 each order are shown by tables giving the number of species found in the 

 rocks of each age. No fev^er than 2600 species of true insects have been 

 found fossil up to the present time. The great majority of these, as well 

 as of myriopods and arachnids, are from the middle tertiary. This great 

 irregularity in the chronological distribution of the fossil forms, which is, 

 of course, due largely to the character of the deposits, is a plain indication 

 that important insect fauna still remain to be discovered. Thus, of the 

 fossil spiders, 31 forms are known from the palseozoic strata, 1 from the 

 mesozoic, and 285 from the tertiary, the great majority of the tertiary 

 forms having been found in the amber deposits of Prussia. 



-y. Prototracheata. 



Development of Cape Species of Peripatus.f — Mr. A. Sedgwick com- 

 mences his third memoir on the development of Peripatus by a brief refer- 

 ence to the criticisms and arguments of Dr. Kennel. In the ectoderm there 

 appear lateral thickenings, which are continuous from somite to somite; 

 the ventral part of these gives rise to rounded elements, which go to form 

 the nervous system ; the elements are formed first in the preoral region 

 and then in the lateral cords ; or, in other words, the nervous system, at its 

 very first appearance, begins in front of the mouth, vrhere it is continuous 

 across the middle line, and it extends backwards, continuously, on either 

 side; the central ganglia give rise directly to the eyes and tentacular 

 nerves, the portions around the mouth become the circumoral commissures, 

 and the hinder portions are the rudiments of the ventral nerve-cords of the 

 adult. A distinction must be drawn between the true body-cavity and the 

 large apparent body-cavity, vrhich may be called the pseudocoele or vascular 

 space ; the adult body-cavity comes entirely from the pseudocoele, and both 

 heart and pericardium are pseudocoelic ; the only products of the entero- 

 coele cavity are the nephridia and the generative glands vrith their ducts ; 

 neither in the embryo nor in the adult do the nephridia open into the 

 pseudocoele, but into a vesicle in each appendage which has been hitherto 



* Bull. U.S. Geol. Survey, No. 31. Cf. Science, ix. (1887) p. 426. 

 t Quart. Journ. Micr. Sci., xxvii. (1887) pp. 467-550 (4 pis.). 



