so 



MYRIAPODA 



CHAP. 



zontal section through the whole length of the heart in a single 

 segment, with the two ostia at each end of the segment and the 

 two arteries in the middle. 



The arteries, when they leave the body, pass into masses of 

 fatty tissue on either side of the heart, and the other figure (Fig. 

 30) is intended to show the artery leaving the heart and penetrating 

 into the fatty tissue. The figure is taken from the same section 

 as the former one, but is much more highly magnified, so as to 

 show more detail. The delicate coats of the heart are shown, 

 the artery being covered with a clothing of large cells. 



ogl. 



Art 



ost 



Fig. 29. Heart of Fig. 30. Heart of Julus terrestris showing structure of 

 Jvlus terrestris artery {Art.) and external coat of heart {ext.c), also fat body- 



showing ostia {ost) {t^b), highly magnified. Ht, The cavity of the heart. The 



and arteries {Art) circular muscle fibres which surrounds the heart are shown 



magnified. just below the external coat {ext.c) ogl, Oil globules of the 



fat body. 



Myriapods breathe by means of tracheae, with the exception of 

 the Scutigeridae, whicli have an elementary form of lung which 

 resembles that of spiders, and will be mentioned further on. 

 These tracheae, as in Insects, are tubes lined with chitin, which 

 is arranged in spiral bands. The tracheae open to the exterior 

 by openings called stigmata, through which they receive the 

 external air, which passes into the main tracheal tubes and into 

 their ramifications, and thus effects the aeration of the blood. 



The nervous system of the Myriapods consists, as in Insects, 

 of a brain, which may be more or less developed, a circum- 

 oesophageal ring embracing the oesophagus, and a ventral chain 

 of ganglia, and in some cases (Newport) of a system of visceral 



I 



