2 divisions. The Monstrilloida are, according to the interesting observations 

 of Malaquin, in their juvenile state true endoparasites, living as simple, sac-like 

 bodies in the blood-vessels of some invertebrate animals (Annelids), whereas 

 in the adult state they are freely living pelagic animals provided with power- 

 fully developed natatory appendages. The Notodelphyoida, on the other hand, 

 are for whole their life confined to their hosts (simple and compound Accidians), 

 all stages of growth being mostly found together in the branchial cavity of these 

 Tunicata. Yet they do not seem, as a rule, to feed on the juices of their 

 hosts, but more properly on the nourishing particles and small organisms 

 introduced, together with the constantly renewed water, in the branchial cavity 

 by the breathing process. Of course they cannot at all be regarded as true 

 parasites, but more properly as commensals or messmates. Both divisions 

 here treated of are well represented in the Fauna of Norway, and as there is 

 some confusion in regard to the exact definition of the genera and species, 

 and moreover the descriptions and figures given by earlier authors in many 

 cases are very incomplete and partly erroneous, I think that a thorough revision of 

 these 2 interesting groups, accompanied by good figures, cannot fail to be 

 of interest. 



