Early in June of this year (1914) I received from the Plymouth Marine Laboratory through the kindness of Dr. E. J. Allen, F.r.s., several Thermos flasks containing quantities of a culture of Luidia in the early blastula stage. This culture was made for me by Mr. James Gray, King's College, Cambridge, to whom, and to Dr. Allen, I desire herewith to express my indebtedness. The larvæ were little the worse of the journey to Glasgow, but it seemed to me that they showed even greater irregularities of form than might have been expected from Mortensen's (13) description of blastula formation in our species. However, in the end, abundance of perfectly typical young bipinnariæ were secured from the contents of the various flasks. The abnormal larvæ became gradually fewer through death, and those which survived could be isolated without much trouble, since they exhibited less capacity for keeping near the surface of the water than their healthier brethren. A great many of the early malformations were of the nature of double or twin formation, and it soon became evident that the teratological type in question, namely, double monstrosity, was about to receive a more varied expression, and to attain a more advanced stage in development, than it had ever before been my good fortune to find in any starfish culture.

In the accompanying illustrations two series of abnormal larvæ are figured, one at the gastrula stage (Figs. 1–11), and the other at that of the early bipinnaria (13–21). As a description is appended to each figure, only questions of general interest need be dealt with here.