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In other instances, the courses which lead from a similar starting-point to a similar goal, separate widely in the middle of the development, as in the Prawns with Nauplius-brood already described. Finally, so that even the last possibility may be exhausted, it sometimes happens that the greatest similarity occurs in the middle of the development.
Species of Peneus live in the European seas, as well as here, and their Nauplius-brood has no doubt repeatedly passed unnoticed through the hands of the numerous naturalists who have investigated those seas, as well as through my own,* for it has nothing which could attract particular attention amongst the multifarious and often wonderful Nauplius-forms.
As the Lernaeae and Cirripedes, on account of their Nauplius-brood, were separated from their previous connexions and referred to the Crustacea, we shall, for the same reason, have to separate Peneus from the Prawns and unite it with the Copepoda and Cirripedia. But the most zealous embryomaniac would probably shrink from this course.
Not unfrequently we might indeed directly reverse the proposition and assert that the difference becomes the greater, the further we go back in the development, and this not only in those cases in which one of two nearly allied species is directly developed, and the other passes through several larval stages, such as the common Crayfish and the Prawns which are produced from Nauplius-brood.
I leave it to our opponents to find them out. Most of them may easily be proved to be only apparent. There are two of these objections, however, which lie so much on the surface that they can hardly escape being brought forward, and these, I think, I must get rid of. But then neither Peneus with its Nauplius-brood, nor even apparently the Palinuri could be referred back to this ancestor.
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