Genera of Uncertain Position. 119 



Mantle and visceral mass not muscular, mantle smooth. 



Mantle opening in adult absent. 



Mesentery rather broad, running in shortest axis of body, irregularly and obliquely to 

 the long axis of host. 



Body cylindrical, immensely laterally expanded so that the axis running from right to 

 left at right angles to the morphological long axis is the actual long axis of 

 the body. 



Ring of attachment at posterior end of mesentery. 



Colleteric glands paired, forming two conspicuous discs on the surface of the vis- 

 ceral mass. 



Nauplius unknown. 



Endoparasitic development unknown. 



Bodies of doubtful meaning but possibly complemental males, fully developed and 

 containing spermatozoa, may be present in the mantle cavity. 



Parasitic on Isopoda (Anthuridae) . 



D. calathurae. Host, Calathura brachiata from Greenland, Forsblads Fjord, 50 fathoms. 

 Diagnosis of species that of genus. 



The discovery of this highly interesting but in some respects problematical genus is 

 due to Dr. H. J. Hansen of Kjobenhavn who noticed the three parasites on the Isopod and, 

 believing them to belong to the Rhizocephala, put two out of the three specimens at my 

 disposal. The investigation of these two specimens both by dissection and serial sections has 

 left no doubt in my mind that we are dealing with an aberrant and probably primitive type 

 of Rhizocephala, but the complete justification of this belief can only be reached by a study 

 of the developmental phases through which the animal -passes. 



The three specimens found by Dr. Hansen and figured on Plate 8 fig. 9 were attached 

 to the ventral surface of their host and lay comfortably protected by the folds of the 

 marsupium. 



The reasons for considering this species a member of the Rhizocephala are as follows — (1) 

 It is clearly a Crustacean, from the presence of chitin lining all the epithelial surfaces. (2) 

 It must be a Cirripede owing to the character of the spermatozoa (Plate 8 fig. 19), which 

 are filamentous bodies staining along their whole length and identical in all respects with 

 the spermatozoa of the Rhizocephala. (3) The numerous special resemblances to the Rhizo- 

 cephala besides the fact of its infecting a Crustacean are found in the presence of a visceral 

 mass containing the ovaries and surrounded by a mantle; the nervous system reduced to a 

 single ganglion and situated near the anterior extremity of the mesentery, the presence of two 

 oviducts modified into colleteric glands, the character of the ova which in all their stages are 

 identical in appearance, with those of the Rhizocephala. The only fundamental difference to 

 the Rhizocephala is found in the apparent absence of a root system and the method of fixation 



