In fig. 2 a great change has set in. There is no distinction between the lateral appendages of the third and fourth segments at left. These two have been fused together, they have united, so as to make the left triangular spine look larger than it was originally. The appendages of the right side are still in the same state as before. But this fusion of the lateral appendages also takes place in another direction, as shown in another specimen (fig. 3), so that the second and third appendages on both sides coalesce into one piece. Now it is easy to imagine that at last a complete fusion has set in between all lateral appendages and that instead of the original three on each side, there is only one large piece, reaching beyond the shell as a broad spine, as represented in the hypothetical figure 4. In the figure 3 a progressive change is also seen in the transformation of the first central segment. From occupying the whole foremost space of the shell it has been lessened in size, more distantiated from the anterior border of the shell and rounded off, more prominent and definite from the lateral appendages, which have become narrow, though of the same length as before. The two first central segments seem to have been united into one. Between the hypothetical figure 4 and fig. 5, there is evidently a great lacuna, not yet filled up. In the interval of time the two appendages, which we saw in fig. 4, have been much modified, the posterior one having lost so much in bulk, and the anterior being lengthened and stretching out beyond the border of the shell in a narrow spine alongside the posterior one. The central segmented part has now assumed a shape, which on comparing it with the following stages of development makes its true nature evident and that it indeed is what in the adult animal becomes the glabella. The meaning of the previous stages then also is easily understood. The central segmental piece in them is the glabella or we may, as BERNARD already has done, call it for rhachis and the side appendages for pleura, as this little larva represents the whole body of the future trilobite, and embodies all its parts _in nuce_. Through the great changes which these pleura undergo, it results, as we have seen, that two pair vanish, being incorporated with the large fourth pair and that only two rest for a while, the anterior one being the so much renowned frontal-lob or eye lobe and the second one the so called »ornamental spine», which in fact is a compound of the original second third and fourth pleura of the corresponding segments. It is to be borne in mind that this larva, which represents the future trilobite in its earliest stage, is nothing but the head, or what in the adult takes the place of the head, and especially its dorsal surface and that it thus solely consists of the future head.