. Chimæroid fishes and their development. Fishes; Chimaeridae. 38 CHIMyEROID FISHES AND THEIR Fig. 23.—Egg-capsule of Rhinochimaera pacifica. (Venlial aspect.) Natural size. Misaki. however, may best be considered subse- quently in correlation with similar facts. The capsules may also be referred to at the present time in the evidence they present regarding the factors of evolution ; for it is clear that such highly specialized capsules provide a valuable check upon the evolutional process from the standpoint of the obvious "prevision" which they demonstrate. The capsul


. Chimæroid fishes and their development. Fishes; Chimaeridae. 38 CHIMyEROID FISHES AND THEIR Fig. 23.—Egg-capsule of Rhinochimaera pacifica. (Venlial aspect.) Natural size. Misaki. however, may best be considered subse- quently in correlation with similar facts. The capsules may also be referred to at the present time in the evidence they present regarding the factors of evolution ; for it is clear that such highly specialized capsules provide a valuable check upon the evolutional process from the standpoint of the obvious "prevision" which they demonstrate. The capsule is, in short, adapted not so much to the egg as to the young fish which it will later contain. Thus it is specialized in accord with the shape of the young fish, its position, and its late physiological needs, all to a de- gree which is, indeed, probably unequaled in the secondary embryonic membranes of other animals.* This degree of special- ization becomes clearer, moreover, when we take into consideration the formation of the capsule. FORMATION OF THE CAPSULE. At the time the egg is about to leave the ovary the oviduct is flaccid and is richly suffused with blood ; in fact, from this time onward the oviducal sinusf in which they lie is dilated (plate i, fig. 4, and plate 11, fig. 5, ovd. jr.), forming a *Cf. Dean, 1904, Biol. Bulletin, vol. vii, pp. 105-112. t These sinuses arise in the mesovaria, the walls of which do not become apposed. They are thus longitudinal sacs of blood in which the oviducts lie more or less freely, depend- ing upon the degree of development of the egg-capsule ((•/'. plate II, fig. 5, and plate i, fig. 4, left oviduct). In the former figure, however, this condition is not seen favorably, since the oviduct is purposely pushed against the wall of its sinus, thus dislodging the opaque blood, so that the structures of the oviduct can be better described. In the latest stage in the formation of the capsule, on the other hand, the sinus is so fille


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Keywords: ., bookcentury1900, bookdecade1900, booksubjectfishes, bookyear1906