208 DR. CARPENTER'S RESEARCHES ON THE FORAMINIFERA. 



other, and will thus favour the partial action of any cause (e. g. an excess of nutrient 

 materials) which promotes a more rapid growth on one side than on the other. And 

 this view is most remarkably borne out by the fact, which I shall more fully illus- 

 trate in a subsequent memoir, that in another example of this group*, which, though 

 normally growing upon the cyclical type, possesses a greater degree of segmental 

 independence, such irregularities occur far more frequently ; so that, in fact, it is rare 

 to meet with a disk whose increase has taken place with uniformity throughout. 



37. Reparation of Injuries. Looking at that vegetative repetition of parts which 

 pre-eminently characterizes the body of the Orbitolite, every one of the segments 

 first budded-off from the nucleus, and subsequently from the margin of the pre-formed 

 zones, being the precise repetition of every other, it may be expected from the 

 analogy of similar organisms, that every one of these parts should be equally capable, 

 both of repairing injuries done to itself, and of maintaining an independent existence 

 when detached from the mass to which it originally belonged. And although no 

 opportunity has yet presented itself, of subjecting such a conclusion to the test of 

 experiments devised for the purpose, yet accident has furnished the means of verifying 

 it, to a degree that could scarcely have been anticipated. For in the course of my 

 examination of the large collections which have been placed at my disposal, I have 

 met with several specimens, in which it is evident that, after larger or smaller por- 

 tions of the disk had been broken away, a new growth has taken place along the 

 fractured edge. Various examples of this are shown in Plate VIII. In the first that 

 I happened to meet with, which is represented in fig. 6, the injury is evidently very 

 slight, being confined to the loss of a few rows near the edge of the disk, for some- 

 thing less than half its circumference (a b). This injury had obviously been sustained 

 previously to the formation of the last two zones ; for these, whilst added to the 

 uninjured part of the margin in the usual way, have followed the irregular contour of 

 the broken edge; and whilst in the former case the cells present their normal con- 

 formity to those of the margin they invest, in the latter, the cells, while obviously 

 continuous with the preceding, are quite unconformable to those of the fractured 

 margin, as is shown on a larger scale in fig. 7- Hence it seems to me probable, that 

 the growth of these two rows along the fractured edge, has taken place, not from that 

 edge itself, but by an extension of the sarcode about to form the new circle of the 

 entire edge, from the points a and b. In fig. 9 is seen an example of a similar kind, 

 in which a much larger portion of the disk has been broken away, so as to leave only 

 an irregular fragment, including its centre and about an eighth of its margin. Here 

 seven rows of cells have been formed since the injury ; and these, whilst produced 

 conformably to those of the uninjured margin, present the most marked want of con- 

 formity to those of the fractured margin, which, nevertheless, they completely surround. 

 A careful examination of this specimen, indeed, seems to me to leave little room for 

 doubt, that the growth of the innermost, or what 1 may call the reparative zone of 



* I refer to a genus hitherto undescribed, which I shall designate Cycloclypeus. 



