The following paper by Dr. Fritz Müller[222] forms the third of a series of communications on Brazilian butterflies published in “Kosmos,” and as it bears upon the investigations made known in the third essay of the present work, I will here give a translation, by permission of the publisher, Herr Karl Alberts. “ACRÆA AND THE MARACUJÁ BUTTERFLIES AS LARVÆ, PUPÆ, AND IMAGINES. “In a thoughtful essay on ‘Phyletic Parallelism in Metamorphic Species,’ Weismann has shown that in the case of Lepidoptera the developmental stages of larva, pupa, and imago vary independently, and that a change occurring in one stage is without influence upon the preceding and succeeding stages, so that the course which has been followed by the individual stages in their developmental history has not been in all cases identical. This want of agreement may manifest itself both by unequal divergence of form-relationship, and by unequal group formation. With respect to unequal form-divergence the caterpillars are sometimes more closely related in form than their imagines, and at other times the reverse is the case. With respect to unequal group formation again, two cases are possible; the larvæ and imagines may form groups of unequal value, the one stage forming higher or lower groups than the other, or they may form groups of unequal size, _i.e._, groups which do not coincide but which overlap. Form-relationship and blood-relationship do not therefore always agree; the resemblances among the caterpillars would lead to a quite different arrangement to that resulting from the resemblances among the imagines, and it is probable that neither of these arrangements would correspond with the actual relationships. “Starting from this fact, which he establishes by numerous examples, Weismann proceeds to show most convincingly that an innate power of development or of transformation, such as has been assumed under various names by many adherents of the development theory, has no existence, but that every modification and advancement in species has been called forth by external influences. “A most beautiful illustration of the want of ‘phyletic parallelism,’ as Weismann designates the different form-relationships of the larvæ, pupæ, and imagines, is furnished by the five genera _Acræa_, _Heliconius_, _Eueides_, _Colænis_, and _Dione_ (= _Agraulis_). This instance seems to me to be of especial value, because it offers the rare case of pupæ showing greater differences than the larvæ and imagines. “The species of which I observed the larvæ and pupæ are _Acræa Thalia_ and _Alalia_, _Heliconius Eucrate_, _Eueides Isabella_, _Colænis Dido_ and _Julia_, _Dione Vanillæ_ and _Juno_; besides these I noticed the pupa of _Eueides Aliphera_.