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ME. W. K. EEOOKS 014 LUCIFEK: 
follows that Metschnickoff studied something else, or that he was in error in 
believing that he had traced his Nauplius directly to what Claus has shown to be a 
somewhat late stage in the development of Euphausia. Metschnickoff’s only reason 
for believing that his Nauplius is a young Euphausia is its resemblance to Claus’s 
larva, and as there is certainly an error here, we are not justified in giving unqualified 
acceptance to his statement that it is an Euphausia larva. It seems very probable, 
indeed, that this is the case, but in the absence of the direct evidence which could only 
be afforded by actually tracing it back to an Euphausia egg, or forwards to the adult 
Euphausia, I do not think that the existence of a Malacostracan Nauplius can be said 
to be established by these observations, for they do not stand the severe test which is 
demanded by their unusual importance, and I think the facts justify the statement 
that, up to the present time, there has been no unquestionable evidence of the 
occurrence of such a stage of development in the higher Crustacea. 
The present series of observations is complete at both ends, and I have not relied 
upon surface-collecting to fill a single gap, but have traced every stage in isolated 
captive specimens, and the possibility of error seems to be entirely out of the 
question. 
The close resemblance between the Nauplius of Lucifer, and Muller’s and 
Metschnickoff’s larvae, renders it almost certain that they also are Malacostracan 
larvae, but before this corroborative evidence was furnished, it was certainly quite 
possible, although hardly reasonable, to doubt whether this was true of either of them. 
II.— The Segmentation of the Egg, and Formation of the Food-yolk and 
Primitive Digestive Cavity. 
Unusual difficulties attend the study of the early stages in the embryology of 
Lucifer, and the observations which I have been able to make are incomplete, and 
leave many gaps to be filled and many interesting points to he decided by future 
investigations ; but the facts which I have made out are so novel, so different from all 
that was previously known of the early stages of Arthropod development, and they 
throw so much light upon the relation of the peculiar and greatly modified form of 
segmentation characteristic of the group to the less modified form of segmentation 
presented by the more normal eggs of other animals, that it seems best to give my 
results in their present incomplete state. 
I am the more willing to do this, because the peculiar difficulties of the subject leave 
little hope for the attainment of more complete results in the future. 
The eggs are so loosely attached to the appendages of the female that they are 
broken off by the slightest roughness of handling, and it is very difficult to obtain them 
by collecting the egg-bearing females. Even when great numbers of mature specimens 
are captured in the breeding season, with the greatest care and delicacy, very few of 
