PLATHELMINTHES 



Somewhat different from Muller's larva, though still derivable from 

 it, is that of Olirtodadus auritus (Fig. 79), which has been carefully 

 studied by Hallez. Like Muller's larva, it also possesses eight lobe- 

 like processes, two of which, however, the median ventral and dorsal 

 ones, have moved far forward. The first one, situated in front of the 



Fig. 78.—^ and B, larva? of Yungia aurantiaca (after A. Lawg) about to change 

 into the worm, seen from the ventral surface. The eyes are indicated for the 

 sake of better orientation. 



mouth, attains a considerable size, so that the anterior end appears 

 spread out like an umbrella. Behind, as in Muller's larva, there are 

 two ventral, two lateral, and two dorsal appendages surrounding the 

 larva. Eigid cilia at the anterior and posterior ends of the body give a 

 characteristic appearance to the larva. 



Goette's larva of Stylochus pilidium resembles Muller's larva less. 

 In it (if we make use of the expressions employed for Muller's larva) 

 the two lobes situated at the sides of the mouth-opening are especially 

 well developed (Fig. 80). The lobe lying in front of the mouth, on the 

 contrary, is less developed, as is also the middle dorsal one. Other 

 appendages are wanting. Inasmuch as the back is arched, this part 

 assumes a bell-shaped appearance, and the larva acquires a resemblance 

 to a Nemertean pilidium, which is increased by the occurrence of rigid 

 cilia. The apex is marked by the dorsal lobe (Fig. 80). The larva in 



