246 THE ANATOMY OF INVERTEBRATED ANIMALS. 



ova are conducted by means of the oviduct, which opens 

 into it. 



On the dorsal surface of each side of the terminal seg- 

 ment of the body there is a tubercle produced into five spines 

 anteriorlv, and carrying, posteriorly, a long and delicate se- 

 tigerous filament (Fig. 63, J5, g). 



The alimentary canal of Apus is very simple, consisting 

 of a vertically ascending oesophagus, which bends back into 

 the small stomach, situated immediately behind the com- 

 pound eyes, in the middle of the region bounded by the two 

 transverse furrows on the dorsum of the carapace ; from the 

 hinder end of the stomach the straight intestine passes back 

 to the anus, which is seated beneath the terminal segment. 

 The liver consists of caeca, which branch off from the stomach 

 and lie on each side of it, in the head. Zaddach describes a 

 pair of glands which he regards as salivary, placed above, 

 and opening into, the stomach itself, like the salivary glands 

 of the Scorpion. 



The heart occupies the tergal region of the eleven ante- 

 rior thoracic somites, presenting as many chambers, with lat- 

 eral venous apertures. 



The nervous system consists of a quadrate cerebral mass, 

 placed immediately under the compound eyes, and giving off 

 large nerves to them and to the remains of the single eye of 

 the larva, which lies in front of their anterior extremities. 

 Commissures pass downward and backward on either side of 

 the oesophagus, and connect the cerebrum with a chain of 

 numerous ganglia placed on the median line of the ventral 

 surface. It is worthy of remark, that the antennary and 

 antennulary nerves are given off from the commissures, far 

 behind the chief cerebral mass. 



In the female, the ova are developed in the caecal branches 

 of two long tubes, situated one on each side of the body, and 

 opening, as above described, in the eleventh pair of append- 

 ages. Apus usually propagates agamogenetically, and the 

 examination of thousands of individuals, extending over more 

 than thirty years, failed to reveal to Von Siebold the ex- 

 istence of a male form. In 1856, however, Kozubowski * dis- 

 covered a small proportion of males (16 in 160), among the 

 specimens taken in the neighborhood of Cracow ; and near 

 Rouen, in 1863, Sir John Lubbock found the largest pro- 



1 " Ueber den mannlichen Apus cancriformis" (" Archiv far Naturge- 

 schichte," 1857.) 



