This paper is a preliminary account of a series of experiments on the hybridization of Echinoids, first commenced by one of our number (De Morgan) at Plymouth in 1909, and which will form part of a larger work now approaching completion. This will comprise the hybridization of Echinus acutus, E. esculentus, and E. miliaris, together with an account of the cytology of the hybrid crosses and the control of paternal and maternal influence by chemical means.

regard to the number of primary mesenchyme cells. He stated that doublefertilized eggs had an unecjual amount of mesenchyme in the two halves of the larvae, and that the mesenchyme was therefore influenced by the sperm. He found that the sperm aflected also the form, size, and pigmentation of the larvpe. In this controversy between Boveri andDRiKSCH it is very difficult to decide which was in the right, as tlie criteria used to determine the dominance were so questionable. Driesch, for example, suggested that BovERl used unhealthy larvas in which to count the mesenchyme cells, or that he counted in other cells with them. Peter (73) attributed these conflicting results to the great individual variation which he found in the number of mesenchyme cells within each species Again, the form of the larvae is a very doubtful point on which to decide the inheritance. Driesch stated that the shape of the larvae was maternal, except when influenced by the skeleton ; but Boveri claimed to have found paternal influence in the shape of very young larvae, before the development of the skeleton. He admits that the shape may be maternal, but Driesch states that it is always so. lu 1906, FiscHEL (27), working at Villefranche, crossed Arhacia jmstulosa, Echinwĥ r-evispinosus and Sti oiigyloceidroUis lividus. In opposition to Driesch, he concluded that tlie hybrids were not purely maternal, but that the sperm had, in many cases, an influence on tlie form, size, pigment, and skeleton. He regretted, liowever, that he

Referate. dagegen (Strong~y/ocentrotus ? x S~haerechinus d, Ec/dJms ? × S2haer. d) wo eine Elimination schon in den ersten Furchungsstadien eintritt, dtirfte die Ursache dazu nicht in idioplasmatischer Disharmonie liegen, was sich daraus ergibt, dab das eliminierte Chromatin keineswegs sofort erkrankt, sondern sich bis in das Blastulastadium hinein erhalten und auch vermehren kann. Es mangelt ihm allem Anschein naeh nur die F~.higkeit, sich in Tochterchromosomen zu trennen, ein Mangel, der mit Idioplasma-Disharmonie nicht in direkter Beziehung stehen diirfte. Dem entsp.richt auch, dab bei der umgekehrten Kreuzung der gleichen Spezies, wo wlr also die gleiehen Idioplasmen verbinden, wo aber jene Chromosomenelimination in den ersten Furchungsstadien fehlt, eine Erkrankung nicht eintritt. Hier vertragen sich somit die Idioplasmen. B a l t z e r. Shearer, Cr., Morgan, Walter de, and Fuehs, H.M. Preliminary notice on the experimental hybridization of Echinoids. (Journ. Mal~ine Biol. Assoc. 9 19II.

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