MORPHOLOGY OF INVERTEBRATE TYPES 



though the number of branches is definite (our species has forty 

 branches, i. e., eight branches for each arm) the method of 

 branching is subject to great variations. Each branch is com- 

 posed of numerous joints, every other joint carrying on its oral 

 surface two many-jointed pinnules or small branches. Not only 

 the branches of the arms but the pinnulae too have an ambu- 

 lacral groove with openings for the ambulacral tentacles devoid of 

 suckers. The ambulacral grooves continue from the two pri- 

 mary branches of each arm onto the oral disc, each pair soon 

 uniting and reaching the mouth in form of a single groove. 

 Radiating from the mouth are therefore only five ambulacral 

 grooves. The anus is also on the oral disc surrounded by ossicles 

 which form a tube-like inclined projection. (Plate III, f. 2 of 

 J. Mtiller. Abh. Ak. Wiss., Berlin, 1841.) Pedicellariae absent. 

 In the internal organization should be mentioned the presence 

 of numerous hydrophone canals opening into the ccelome, ab- 

 sence of Polian vesicles and the position of the gonads in the 

 pinnulae with genital rhachis running through the whole length 

 of the arm branches. The reproductive cells reach the outside 

 through the rupture of the tissues of the pinnulae in more or less 

 predetermined places. The development is not known, but is 

 probably similar to that of the European crinoid Antedon. 



