788 SUMMARY OF CURRENT RESEARCHES RELATING TO 



revived from " earth " taken from Durwaston, says * that it was 

 simply the dust of the garden which happened to deposit itself in 

 certain cup-like receptacles made artificially of a substance which 

 coated itself with an oxide, giving to the dust when wet a rusty 

 appearance. After having been in a drawer for more than three years 

 no symptom could be detected of a decrease in the number or activity 

 of the stock. He adds, " It is to me inexplicable that although I 

 have collected very many specimens of the rotifer (JR. vulgaris) from 

 plants taken from ponds, I never could acclimatize these in my tanks, 

 so that they would bear the drying process so successfully as when 

 procured after my own fashion." 



Echinodermata. 



Heteractinism in Echinodermata.t — In dealing with a small col- 

 lection from Point de Galle, Professor F. Jeffrey Bell describes a 

 specimen of Ophiomaslix annulosa in which one arm measures as much 

 as 300 mm. in length, and gives an account of another example, which, 

 as he calculates, may have had a total spread of 800 mm., or nearly 

 32 inches. He points out that such a form must be continually sub- 

 jected to the loss of part of an arm, but that owing to vegetative 

 repetition the loss will hardly perhaps affect the individual, and not at 

 all the species. Contrary to the opinion of such observers as Haeckel 

 and Simroth, he holds that such external irritation is not to be neglected 

 in discussing the question of heteractinism. There would appear to 

 be in all echinoderms a capacity for self-injury, which, in these days, 

 is excited by pain, fear, or anger ; while the starfish may only throw 

 off an arm, an ophiurid, in consequence of its greater centralization, 

 undergoes fission of the disk. The disk thus injured may give birth 

 to more arms than it has lost ; and when this habit becomes inherited, 

 we may get six- rayed forms ; such are to be found in Ophiacantha, 

 where, in some cases, there is so well-marked a cenogeny that, not 

 only are the adults sex-radiate, but the young are developed vivipar- 

 ously, and never exhibit any bilateral symmetry. 



The origin of this tendency to self-mutilation is ancient and deep- 

 seated, for some polyactinic forms (Brisinga) lose their arms for the 

 purpose of setting free their genital products; the tendency would 

 seem to be lost in those which, by the power of the spines, are able 

 to resist all foes, or those which by their capacity for vegetative 

 repetition are enabled to atone for it. When the tendency is seen in 

 others it has quite a different physiological significance, for the result 

 is true asexual reproduction. 



Considerably modifying a table once given by Haeckel, Professor 

 Bell points out that in the Echinodermata we may have — 

 A. Sexual reproduction. 



a. With metamorphosis (" metagenesis and internal gem- 

 mation "). 

 /?. Without metamorphosis (viviparous Echinodermata). 



* Times, 4th October, 1S82. 



t Anu. and Mag. Nat. Hist., x. (1882) pp. 21S-25. 



