64 MR. W. K. BROOKS ON LUCIFER: 



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 

 larvte, 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 be 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 



