200 Mr. F. G. Sinclair. [Nov. 26, 



absolu. En effet, nous avons neglige les carres des et des // et rien 

 ne prouve qu'en tenant compte de ces carres, le resultat ne serait pas 

 change. Mais nous pouvons dire au moins qne les et ?/, s'ils sont 

 originairement tres petits, resteront tres petits pendant tres long- 

 temps. Nous pouvons exprimer ce fait en disant qne la solution 

 periodique jouit sinon de la stabilite se'culaire, du moins de la stabilite 

 temporaire" Here the conclusion of 9 of my present paper is per- 

 fectly anticipated, and is expressed in a most interesting manner. 

 M. Poincare's investigation and mine are as different as two investi- 

 gations of the same subject could well be, and it is very satisfactory to 

 find perfect agreement in conclusions. 



II. "A new Mode of Respiration in the Myriapoda." By 

 F. G. SINCLAIR (formerly F. G. HEATHCOTE), M.A., Fellow 

 of the Cambridge Philosophical Society. Received August 

 12, 1891. 



(Abstract.) 



The Scutigeridae respire by means of a series of organs 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 off ; 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 surround- 

 ing 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 gly- 

 cerine, they can be seen to be filled with air. The tubes each branch 

 several times. Each tube is lined with chitin, which is a continua- 

 tion 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. 



Reasons for supposing these Organs to le Respiratory, 



1. There are no other organs which could be supposed to be respi- 

 ratory in function. 



2. The tubes are chitinous, and the chitin grows thin and mem- 



