2G4 Miscellaneous, 



Ilea sons for supposing/ these Orr/mis to he Respiratory. 



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

 respiratory in function. 



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

 branous towards the end, affording a good opportunity for interchange 

 of gases. 



;i. The tube ends project into the pericardium, so that they arc 

 bathed with the blood. 



4. The tubes are filled with air. 



"). The organ is so placed as to aerate the blood just before it 

 returns to the heart. 



0. In Scutigora the dorsal scales do not agree in number with the 

 legs. The organs are arranged on the dorsal scales : that is they 

 are not arranged in correspondence with the mesoblastic or primitive 

 segmentation (see a fonner paper before this Society, '• The Post- 

 Embryonic Development of Jul us terrestris" 1888). This renders 

 it prolsable that they are not a primitive development, but a recent 

 modification, agreeing with the fact that all other Myriapods breathe 

 by the more primitive method of tracheae. 



This mode of respiration differs from that in other Mj-riapods in 

 the following i)articulars : — 



1 . The tubes are collected into one definite organ, instead of being 

 distributed about the body. 



2. The tubes have no spiral thread. 



.'}. In acting on the blood just before it returns to the heart, so 

 that aerated blood is distributed instead of unaerated. 



It resembles the trachea; of other !Myriapods in the following 

 jiarticulars : — 



1. In the air-sao into which the tubes open. 



2. In the cylindrical form of the tubes, 

 ti. In the branching of the tubes. 



'J'he organs resemble the tracheal lungs of Spiders — 



1 . In the largo air-sac. 



2. In the number of tubes opening into an air-sac. 



3. In the arrangement for bathing the tabes with blood in a 

 blood-sinus. 



4. In the supply of aerated blood by the heart. 

 They differ from them in — 



1 . The form of the tubes, wliicli in Scutigera are cylindrical. 



2. In the absence of the membrane which in Spiders surround;' 

 the organ. 



I therefore hold that the respiratory organ in Scutigera holds a 

 position intermediate between tlie tracliea^ of ilyriapods and the 

 lungs of Spiders. I hold with A. Leuckart (' Zoitscb. fiir wiss. 

 Zool.' vol. i. p. 24*), 1849, '' Ueber den l^au und I^edoutung der sog. 

 Lungon bei den Aracbniden *') that the trachea^ have develoj^ed into 

 the lungs of Spiders and Siorpions, and I think that the organs in 

 c|Uestion form a series of which the lowest term is the trachea\ the 

 next the organ of Scutigera, then the lungs of Spiders, and then of 

 Scorpions.— A-oc. Roy.Soc. No. 303, pp. 200, 201 (Nov. 20, 1801). 



