112 THE PINEAL ORGAN 



which are seen to be inserted into the basement membrane of the skin. 

 These movements can be made in all directions, including rotation, as 



Fig. 74. — Early Stages in the Development of Astacus Fluviatalis, showing 

 the Relation of the Ocelli to the Protocerebrum. 



at. 1 : antennule. lab. : labrum. 



at. 2 : antenna. 



at. 1 g. : ganglion of antennule. 



car. : fold which becomes edge of 

 carapace. 



caud.j. : forked extremity of ab- 

 domen. 



mandible, 

 first maxilla, 

 second maxilla, 

 ocellus. 



protocerebrum. 

 th. abd. : rudiment of 

 abdomen. 

 (From MacBride after Reichenbach.) 



m.n. 

 mx. 1 

 mx. 2 

 oc. 

 pr. c. 



thoraco- 



evidenced by the transverse direction of some of the fibres cut in cross- 

 section and the spiral twist of the optic nerve. 



THE EYES OF PERIPATUS (ONYCHOPHORA) 



Peripatus is a caterpillar-like animal which, although generally classed 

 among arthropods, differs from these in certain important respects and it 

 is regarded as intermediate in type between the Arthropoda and Annulata. 

 The paired lateral eyes of Peripatus (Fig. 75) are very similar to those of 



