_Text Book_, 449.) While this fact is congruous with the hypothesis here maintained, it is incongruous with the hypothesis that the annelid was originally an elongated creature which afterwards became segmented; since in that case the implication would be that the cœlomic septa, not arising from recapitulation of an ancestral structure, but originated by the process of segmentation, were first superfluously formed and then destroyed. Various lines of evidence thus converge to the conclusion that an annulose animal is an aggregate of the third order. In June, 1865, when No. 14 of my serial containing the foregoing chapter was issued, I supposed myself to be alone in holding this belief respecting the annulose type, and long continued to suppose so. Over thirty years later, however, in M. Edmond Perrier’s work, _La Philosophie Zoologique avant Darwin_, I found mention of a lecture delivered by M. Lacaze-Duthiers at the École Normale Supérieure in Paris, and reported in the _Revue des Cours Scientifiques_ for January 28, 1865, in which he enunciated a like belief. Judging, however, by the account of this lecture which M. Perrier gives (he was present), it appears that M. Lacaze-Duthiers simply contended that this view of the annulose structure as arising by union of once-independent units, is suggested by certain _à priori_ considerations. There is no indication that he assigned any of the classes of facts above given, which go to show that it _has_ thus arisen. For further facts and arguments concerning the genesis of the annulose type, see Appendix D 2.] CHAPTER V. THE MORPHOLOGICAL COMPOSITION OF ANIMALS, _CONTINUED_.