The inner or hyaline membrane of the fertilized egg of the sea urchin, Strongylocentrotus purpuratus, which serves to hold the blastomeres together, is rendered permanent by keeping the developing eggs in a solution composed of 35 cc. sea water + 15 cc. 3/8 M Ca Cl2. Such cultures show the following facts: (1) The outer or fertilization membrane around the inert blastula disappears normally, i. e., within 24 hrs. It is therefore not broken by the hatching blastula, as is generally supposed. (2) So long as the larvae remain within the Ca-membrane they retain the form of blastulae, but segmentation goes on, and eventually the blastocoel is filled with mesenchyme cells; invagination does not occur. (3) After 3 to 5 days the larvae burst the membranes by pressure; the point of breaking has no reference to the axis of the animal. (4) After escape, the larvae invaginate and form more or less abnormal plutei; the insoluble membranes lie about on the bottom of the dish. The fertilized eggs of the sand urchin, Dendraster eccentricus, since they have no hyaline membrane, do not show similar reactions. In the calcium sea water solution they develop normal gastrulae and plutei only a little more slowly than the controls. In this sand urchin, therefore, the blastomeres must be held together by a mechanism different from that of the sea urchin. If the fertilized eggs of sea urchin are put into sea water which has been brought to pH 3.5 by means of HCl, the hyaline membrane disappears, and in the course of a few minutes the perivitelline space becomes filled with hyaline droplets exuding from the cytoplasm. In volume the droplets may come to equal three-fourths the volume of the cytoplasm, but neither the diameter of the tgg (.072 mm.) nor of the sphere enclosed by the outer membrane (.098 mm.) is immediately altered. Therefore the droplets must largely consist of the sea water of the perivitelline space transferred into the droplets, presumably by osmosis.
Two new cases of hermaphroditism in sea urchins are described. In a search for causative factors of bisexuality, a survey of incidence of the phenomenon in echinoids, both as to genera and geographical distribution, has been made. The suggestion of seasonal dimorphism is rejected.
1. The ions of Ca and K condition general luminescence, and are therefore necessary to the conduction of the impulse. 2. In van't Hoff's solution from which Mg is omitted, Berœ shows hyperirritability with respect to luminescence. This is the result of the action of Ca and K ions unantagonized by Mg. 3. The luminescent material spread on filter paper does not show luminescence in sea water, NaCl, MgCl2, or saccharose solutions isotonic with sea water. In solutions of CaCl2, SrCl2, BaCl2, KCl, and K2SO4 the indicator paper glows with a bright luminescence. 4. In dark adapted Berœ, luminescence is inhibited by a certain quantity of light. This quantity has an average value of 57,285 meter-candle-minutes, which is twelve times the value given by Mnemiopsis.
MOOREprove to be more sensitive to explosive shocks than those without swim- bladders, and experiments showed that a half stick of dynamite may be exploded within 3 feet of a small shark, which has no swim-bladder, without producing any apparent injury.This also applies to a lesser degree to such teleosts as lack swim-bladders.Dr. S. C. Ball kindly dissected some of the fishes with swim-bladders which had been killed
'%3e%3ccircle r='20' fill='%23008'/%3e%3ccircle r='17.5' fill='%23fff'/%3e%3ccircle r='3.5' fill='%23008'/%3e%3cg id='d'%3e%3cg id='c'%3e%3cg id='b'%3e%3cg id='a' fill='%23008'%3e%3ccircle r='.875' transform='rotate(7.5 -8.75 133.5)'/%3e%3cpath d='M0 17.5.6 7 0 2l-.6 5L0 17.5z'/%3e%3c/g%3e%3cuse xlink:href='%23a' transform='rotate(15)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(30)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='rotate(60)'/%3e%3c/g%3e%3cuse xlink:href='%23d' transform='rotate(120)'/%3e%3cuse xlink:href='%23d' transform='rotate(-120)'/%3e%3c/g%3e%3c/svg%3e)
