IN experiments on the power of multiple development of the ovum the result has been reached, that a portion of less volume than one-fourth that of the normal ovum does not possess the capacity of producing an embryo or larva, though it may a gastrula (see postscript); while a portion equal to one-fourth or more of the volume of the normal ovum may, under suitable conditions, produce a gastrula and finally a larva of corresponding relative bulk. This result has been attained by Loeb,l Wilson,2 Driesch,a Morgan) and Zoja.5 Wilson found only a single larva of Amphioxus of one-fourth the normal size and that showed several defects ; and Driesch has not, so far as I am aware, mentioned any pluteus of 'less than one-quarter size. Morgan has recently published the results of his studies on the power of multiple development of the echinoderm ovum. I n this he shows that "the volume of the smallest gastrula which can be produced from fragments of the egg falls below & the volume of normal gastrulae. The volume of the fragments of the egg which produced such gastrulae, varies between & and & of the volume of the ovum." (Summary p. 124 Zoc. cit.) But these smallest gastrulae were unable to