174 MR. LUBBOCK ON SOME OCEANIC ENTOMOSTRACA 
not merely as artificial helps to classification, but as actual groups between which no 
links are known or will ever be discovered. I have already pointed out certain species 
which seem to prove the incorrectness of this opinion, and I shall have occasion in the 
present paper to describe more than one species apparently intermediate between two 
genera. Indeed, so far from considering such links as rare, it would be more correct to 
say that every species is a link between other allied forms. The same argument is ap- 
plicable to species. Of course, as long as any varieties remain undescribed there will be 
gaps — which, however, exist only in our knowledge, and not necessarily in nature. How 
many centuries must elapse, even under the most favourable circumstances, before all the 
existing animals are known to us ; and even then how small a proportion will be described 
of the animals which have peopled the world during the countless ages of past time ! How 
worthless, then, is the argument against the mutability of species which depends on the 
supposed absence of *' links !" "When every variety which now exists, and every one which 
ever has existed, is known, then, and not until then, can this argument be considered con- 
clusive. Moreover, it is admitted by every one that there are certain species which are 
especially variable, that is to say, which present two or more extreme forms, with all the 
intermediate gradations. Now we may fairly ask those who assert that no two species 
are connected by links, how they would separate the instances of variable animals 
(which they admit to occur) from the case which they say does not exist. If we were to 
obtain to-morrow all the links between any two species which are now considered distinct, 
no one can deny that the two would at once be united, and would hereafter appear in our 
classifications only as one variable species. In fact, therefore, they first unite into one 
species all those forms, however different, between which a complete series of links is 
known, and then argue in favour of the permanence of species because no two of them are 
united by links. 
As bearing on this point, I may also mention that there are in the collection about 
ten or twelve other species, represented each by very few (perhaps only one or two) speci- 
mens, which , I can neither refer with sufficient confidence to any already known, and 
which yet differ so little that I cannot venture to describe them as new. I have there- 
fore put them aside for future examination, either when I have more specimens for 
examination, or when the old species in question are better known. I do not see what 
else I could have done; but in this way, no doubt, it comes to pass that specimens 
which can be decidedly determined are named, and the doubtful forms, in which perhaps 
many interesting series of links lie concealed, are left for re-examination at that more 
" convenient season " to which naturalists, like other people, are only too apt to defer any 
inconvenient duty. 
A good example of an intermediate form is presented to us by the species which I have 
named Calanus latus. This species possesses some of the characters of Uuckata, and 
others (more numerous) which induced me to place it in Calanus. The maxillipeds 
resemble those of Eucliceta, and are quite unlike the form which prevails in the immense 
majority of Calani. The long setae with which the anterior antennae are provided, and 
the long seta at the apex, are also similar to those of Mtchceta ; but, on the other hand, 
the form of the front part of the cephalothorax, and the absence of long caudal setae, 
