590 



F. A. Potts, 



peduncle and tlie posterior coiinection of tlie lacuna witli the visceral 

 mass (its course being also complicated by the lateral revolution of 

 the visceral mass). 



The glands of the visceral mass, it may be noticed in Fig. L, 

 occupy a Position whichjustifies their Identification as colleterial glands. 

 It is unfortiinate that the presence uf a gauglion has not been 

 detected in Mycetomorpha. 



9' 

 ■ -ped 



Fig. L. Diagram of Peltogaster 

 seen from the dorsal snrface. 



Fig. M. Diagram of Myceto- 



morjiha seen from the dorsal sur- 



face. Course of the lacuna of the 

 root- System iudicated in red. 



c. gl colleterial gland. yl glauds 

 of visceral mass. g ganglion. 



Other abbreviatious as in other 

 figures. 



The arrows in Fig. M represent 

 the directions of torsion. 



Fig. L. 



Fig. M. 



Sylon is the only other member of the order which is parasitic 

 on shrimps but in spite of this community of habitat there is little 

 resemblance betvveen the two forms for Sylon is the most symmetrical 

 Rhizocephalan and is distinguished from its relations by the presence 

 of two mantle openings. The one character they may have in 

 common is reproduction by parthenogenesis. 



Two little known genera of Rhizocephala agree wdth Myceto- 

 morpha in the presence of Cypris larvae in the mantle cavity. These 

 are Thompsonia (Kossmann 4) on Melia and Sesarmaxenos recently 

 described by Annandale (1) from freshwater crabs. But though 

 the three forms possess a development accelerated by the suppression 

 of the Nauplius stage there are no other features of structure or 

 biology which indicate close relationship. 



The homology of the glands of Duplorhis and jMijcetomorpha has 

 already been discussed. The thinness of the mantle and the poverty 

 of connective tissue in the visceral mass are other points in common. 

 Mr. Smith suggested to mo that the lacuna described in Mycetomorpha 

 resembles the mesenteric canal of Duplorhis. But the lacuna does 

 not open into the mantle cavity and is not lined by an epithelium or 

 chitinous layer but is connected with a rootsystem. 3iycetomorpha 

 then can scarcely be regarded as helping to bridge the gap between 

 Duplorhis and the Rhizocephala with a typical rootsystem. 



