tions of the sarcode body. Hence it is readily conceivable how a canal-system may be formed with considerable regularity in an organism in which the intermediate skeleton attains a considerable development, whilst it may be wholly or partially deficient in another, in which that supplemental deposit of calcareous matter has taken place to a much smaller extent. And it is to be specially observed that all those forms in which it is at present known to attain its greatest completeness, are those tropical or semi-tropical types, in which the influence of warmth, abundance of food, and other external agencies in promoting development, appear specially to favour the largest growth and the most specialized evolution of the Foraminiferous type.
The relations of the forms belonging to the family Miliolitidæ have recently been investigated by Mr. W. K. Parker;[1] and his results are in perfect accordance with my own. Thus in each of the genera Cornuspira, Hauerina, and Vertebralina, Mr. Parker reduces all the reputed species to one; while he shows that even their generic differences are really but of small account. And he not only in like manner reduces all the reputed species of the genus Milola to the level of varieties, but brings down to the same rank the reputed genera Spiroloculina, Biloculina, Triloculina, and Quinqueloculina; the differences between which, arising from asymmetrical growth, and from variations in the form and number of the chambers, cannot be regarded as even of specific value, the Milioline plan of construction being preserved throughout. In the large group of Nodosarinæ which has been carefully studied by Messrs. T. Rupert Jones and W. K. Parker,[2] those gentlemen have felt themselves justified, on the like grounds in reducing a multitude of reputed genera and species to a single type. Between the nautiloid Cristellariæ and the straight moniliform or rod-like Nodosariæ, which agree in essential characters of structure and mode of growth, they find such a continuous series of connecting links, that no line of demarcation can be anywhere drawn, the straight, the curved, and the spiral forms passing gradationally one towards another; and the extreme forms being thus brought together, the various intermediate grades which have been distinguished by systematists under the generic names Glandulina, Lingulina, Dentalma, Rimulina, Vaginulina, Planularia, Marginulina, Dimorphina, Flabellina, and Frondicularia, necessarily fall into the same category.
The same general doctrine having thus been shown to hold good in regard to all the chief natural subdivisions of the Foraminiferous group, it is not my purpose at present to prolong the inquiry in this direction. The systematic study of this tribe needs to be prosecuted far more extensively than my own time and opportunities have admitted, to enable even an outline scheme to be framed, which should represent an approach to the true relations of its principal families. But I think I
