PAHACOKOTOC'A AKERMANl (wARREn). 327 



fat-body. Where there is considerable pressure there tlie 

 hypoderniis is mostly thin and the cuticle is also thin. It 

 may be readily understood that a thin, stretclied hypodermis 

 would only be capable of secreting a thin cuticle. It is clear 

 that the varying thickness of the general cuticle depends 

 partly on this effect of internal pressure. 



Heart. — The heart proper lying within a pericardium is 

 exceptionally short ; it appears to be confined to segments 

 VI and VII in the refiexed abdomen. Anteriorly the heart 

 is continued into a uniform dorsal aorta which bends on itself 

 and runs forward immediately above the oesophagus as far as 

 the procerebral lobes (PI. XVIII, H). The restriction of the 

 heart proper to the refiexed portion of the abdomen is doubt- 

 less associated with the sharp bend contracting the dorsal 

 surface of the anterior abdominal segments and the pressure 

 exerted by the hypertrophied organs. 



In Termitomimus the heart proper is even shorter than 

 in Paracorotoca; it appears to be confined almost entirely 

 to segment VI and a portion of VII; both anteriorly and 

 posteriorly it communicates with a well-defined narrow aorta. 



Muscles. — The musculature has not been especially in- 

 vestigated, but the most characteristic feature is the ext)"a- 

 ordinary development of muscle around the convoluted vagina. 

 These muscle-fibres are mainly transverse and form a very 

 strong investment. It is extremely probable that this great 

 muscular development is associated with the birth of relatively 

 large vivipai'ous young (PL XVIII, fig. 45, m. s. ; PI. XX, 

 fig. 78, m.). The muscular systems of the ejaculatory duct 

 and of the sucking pharynx are also much developed. 



Genital Organs. — Male. — These organs are greatly hyper- 

 trophied. There are two large testes ; the left is pushed in 

 front of the right, and they occupy a large portion of the 

 cavity of the inflated abdomen. Each testis consists of a 

 number of large follicles which dehisce inwardly into wide 

 channels opening into a central cavity (PI. XVI, fig. 19 ; 

 PI. XX, fig. 73, s. ch.). From the central cavity of each testis 

 there arises a narrow, short vas deferens (PI. XIX, fig. 63, s. d.). 



