Nauplius Stage of Praions. 81 



tion unanswered, What can be the parent of Fritz Muller's 

 Nauplius ? 



Why may it not be the larva of a Schizopod or of one of the 

 parasitic Suctoria ? Tlie history of the development of neither 

 of tliese has been worked out. 



MetsclmikofF states that Euphausia belongs to those Podoph- 

 tlialma that pass throug-h a NaujjUus condition. He says 

 (Zeitschr. f. wissensch. Zoologie, vol. xix. p. 479), "that this 

 Schizopod, in one stage of metamorphosis, has two pairs of 

 swimming-feet, a peculiar carapace characteristic oiEuphausia^ 

 and only the rudiments of the oral appendages and pleon. 

 Although I knew but this single stage in the development of 

 Euphausiaj I was yet convinced that it by no means repre- 

 sented the earliest form of larva as it quits the ovum. I could, 

 however, only hypothetical ly point to a six-legged transparent 

 Nauplms as being the earlier larval condition of Euphausiay 



This supposition he confirmed in a paper in the same journal 

 in 1871, where he stated " that the year previously, being at 

 Villafranca, he had the opportunity of examining a consider- 

 able number of freely-swimming Euphausia-lsirvx ;" and he 

 further adds, " besides the larvse which were in various stages, 

 I fished up with Muller's net ova from which the larvae were 

 just ready to escape." The statement that he caught the 

 Nauplii as fi*ee-swimming animals, and captured the ova 

 with a net, raises a question in the mind yet as to the relation 

 of the ova and freely-swimming Nauplius with their parent. 

 But as I presume that Euphausia must have been present or 

 MetschnikofF would not so positively have asserted their con- 

 nexion, and as we are not aware of any Crustacea that deposit 

 their ova until they hav<e liberated the larvee, we must suppose 

 that in taking the one he captured the other. The ova of the 

 ►Schizopoda being carried in a sac-like pouch and not attached to 

 the pleopoda, as in the prawns, larvae might be liberated in 

 unequal degrees of development — altliough he says that, when 

 the larv£e pass into an older stage, " all the larvae of this last 

 stage examined by me have lost with their moulting the in- 

 dented margin to the carapace, which shows tliat I had to do 

 with another species than Euphausia Mulleri (Glaus)." 



As far as the observations of all carcinologists enable us to 

 decide, the form of larvae, within generic relationship of their pa- 

 rents, is identical in all species. It may be fairly assumed that 

 Claus's specimens, which were captured independently in the 

 Atlantic, may be the young of some other nearly related Schi- 

 zopod. 



That Euphausia and its allies may pass through an imma- 

 ture stage like Nauplius is what might, though not generally 



Ann. & Mag. N. Hist. Ser. 5. Vol. ii. 6 



