326 THE ANATOMY OF INVERTEBRATED ANIMALS. 



to the three ganglia placed in the twelfth to the fourteenth 

 somites. There are four ganglia in the abdomen, two dis- 

 tinct cords passing from the last to its extremit}'. The vis- 

 ceral nervous system is represented by an oesophageal gan- 

 glion receiving roots from the cerebral ganglion, and giving 

 branches to the alimentary canal. 1 



Two lateral ovarian tubes, connected by transverse anasto- 

 moses with a median tube, end in two oviducts, which open 

 by a fusiform vagina on the first free sternum (ix). The tu- 

 bular testes end in a pair of deferent ducts, on which, before 

 their union at the common orifice, two long and two short 

 caeca are found, the former playing the part of vesiculae semi- 

 nales. Both male and female organs lie imbedded in the 

 hepatic mass in the posterior thoracic region, their ducts pass- 

 ing forward. Partial yelk-division takes place, and the ova 

 undergo development within the ovarian canals, in a manner 

 which is very similar to that of Astacus. Thus there is no 

 metamorphosis, and the young differ but little from the adult 

 in any respect but size. 



The Pseudo-scorpions ( Chelifer, Obisium) resemble the 

 Scorpions in form and in the nature of their appendages, but 

 they have no aculeate telson nor poison-gland. They possess 

 silk-glands, which open close to the genital aperture, and their 

 two pairs of stigmata are connected, not with pulmonary sacs, 

 but with tracheal tubes. According to Metschnikoff, the eggs 

 undergo complete yelk-division, and the young leave the egg 

 provided only with that pair of appendages, which become the 

 pedipalpi. 



In the number of the appendages, and in the segmenta- 

 tion of the abdomen, Galeodes (or Solpugd) agrees with the 

 Scorpions and Pseudo-scorpions. But the three somites which 

 bear the three hinder pairs of ambulatory limbs (vi, VII, vm, 

 in the Scorpion) retain their distinctness, and there is no 

 cephalo-thorax, in the proper sense of the word. In form and 

 function the pedipalps resemble the first pair of ambulatory 

 limbs, while the chelicerae are subchelate. The organs of res- 

 piration are tracheal. 



The PhalangidoB (Phalangium, Gonyleptus) have chelate 

 chelicerag, but the pedipalps are filiform or limb-like, and the 

 articulated abdomen is relatively short and broad. They have 

 no silk-glands, and their respiratory organs are tracheal. 



i Newport, " On the Structure, etc., of the Nervous and Circulatory Systems 

 in Myriapoda and Macrurous Arachnida." (" Philosophical Transactions," 

 1843.) 



