Miscellaneous. 2G3 



dorm. When the blastoderm has thus fjivcn liirth to the rncsoderm 

 and eiidodcnii, it persists as a siini)lo cellular layer around the layers 

 ■which arise from it, and constitutes the ectoderm. In short, the 

 primitive blastoderm is alone the origin of tlie three layers ; the cells 

 of which it is composed multiply rapidly, and group themselves in 

 two different ways ; some remain at the periphery and will form 

 part of the ectoderm, while the rest ])enetrate into the ovule and 

 represent a meso-eudoderm, which will differentiate into the two 

 final inner layers. 



One of the most important facts is the diifuse genesis of the meso- 

 derm by almost the entire blastoderm ; a second is the double origin 

 of the cndoderm, the two original zones being separated by a vast 

 space. These two peculiarities taken together are really charac- 

 teristic, for we do not meet with them in the condensed developments 

 of the rest of the Coilomata. llnally, a concluding phenomenon of 

 great value is presented by the enteron or primitive intestine, which 

 hollows itself out in the interior of the embryo without in any way 

 jiioceediug from a gastrular invagination, and docs not even present 

 a trace of such a primordial origin ; here, again, is a contrast to the 

 condensed developments of the other Coelomata. At the present 

 moment I am continuing my investigations and extending them to 

 the rodophthalmata ; 1 shall shortly have occasion to show that they 

 exhibit the same phenomena as the Edriophthalmata, and that the 

 blastodermic depressions, considered by divers authors, by Keichen- 

 bach and liobretzky among others, as gastrular invaginations, have 

 not, in reality, such a significance. — Comptes liendus^ tome cxiii. 

 no. 24 (December 14, 1891), pp. 868-870. 



A mw Mode of Respiration in the Mi/riapoda. By F. G. Sinclair 

 (formerly F. G. HEAxncoTE), il.A., FeUow of the Cambridge 

 Philosophical Society. 



The Scutigeridte respire by means of a series of oi'gans arranged 

 in the middle dorsal line at the posterior edge of every dorsal scale 

 except the last. 



Each organ consists of a slit bounded by four curved ridges, two 

 at the edges of the slit and two external to the latter. The slit 

 leads into an air-sac. From the sac a number of tubes are given 

 oft' ; these tubes are arranged in two semicircular masses. The ends 

 of the tubes project into the pericardium in such a manner that the 

 ends are bathed in the blood and aerate it just before it is returned 

 into the heart by means of the ostia. In the living animal the 

 blood can be seen through the transparent chitin of the dorsal 

 surface surrounding the ends of the tubes ; and in the organ and 

 surrounding tissues cut out of a Scutigera directly it is killed, the 

 blood-corpuscles can be seen clustering round the tube ends. If the 

 mass of tubes of a freshly killed specimen are teased out under the 

 microscope in glycerine, they can be seen to be filled -sA-ith air. The 

 tubes each branch several times. Each tube is lined with chitin, 

 which is a continuation of the chitin of the exo-skeleton. Each 

 tube is also clothed with cells, which are a continuation of the 

 hypodermis. The tubes end in a blunt point of very delicate chitin. 



