3. The optic chiasma, thus far characteristic of Ganoids as distinct from Teleosts, may have no great value. It is urged that in closely related species of lizards some have the optic chiasma and others do not. This, however, proves nothing as to the value of the same character among fishes. 4. The transition from Ganoids to Teleosts is of much the same character as the transition from spiny-rayed to soft-rayed fishes, or that from fishes with a duct to the air-bladder to those without such duct. Admitting all this, it is nevertheless natural and convenient to retain the Ganoidei (or _Chrondrostei_ if the older name be discarded on account of the many meanings attached to it) as a group equivalent to that of _Teleostei_ within the class or subclass of _Actinopteri_. It comprises the transitional forms between the _Crossopterygii_ and the bony fishes, and its members are especially characteristic of the Mesozoic age, ranging from the Devonian to the present era. Of the extensive discussion relating to this important question we may quote two arguments for the retention of the subclass of Ganoids, the first by Francis M. Balfour and William Kitchen Parker, the second from the pen of Theodore Gill. Balfour and Parker ("Structure and Development of Lepidosteus," pp. 430-433) thus discuss the =Systematic Position of Lepidosteus.=—"Alexander Agassiz concludes his memoir on the development of _Lepidosteus_ by pointing out that in spite of certain affinities in other directions this form is 'not so far removed from the bony fishes as has been supposed.' Our own observations go far to confirm Agassiz's opinion. "Apart from the complete segmentation, the general development of _Lepidosteus_ is strikingly Teleostean. In addition to the general Teleostean features of the embryo and larva, which can only be appreciated by those who have had an opportunity of practically working at the subject, we may point to the following developmental features[2] as indicative of Teleostean affinities: "(1) The formation of the nervous system as a solid keel of the epiblast. "(2) The division of the epiblast into a nervous and epidermic stratum. "(3) The mode of development of the gut. "(4) The mode of development of the pronephros; though the pronephros of _Lepidosteus_ has primitive characters not retained by Teleostei. "(5) The early stages in the development of the vertebral column. Footnote 2: The features enumerated above are not in all cases confined to _Lepidosteus_ and Teleostei, but are always eminently characteristic of the latter. "In addition to these, so to speak, purely embryonic characters there are not a few important adult characters: "(1) The continuity of the oviducts with the genital glands. "(2) The small size of the pancreas, and the presence of numerous so-called pancreatic cæca. "(3) The somewhat coiled small intestine.