LEPTOMEDUS.E POLYORCHIS, SPIROCODON. 



219 



Bancroft, 1904-06, carried out an interesting series of observations upon the galvanotropic 

 reactions of the medusa, showing; that the tentacles and manubrium respond definitely to the 

 current, even detached parts ot the tentacles reacting. The maximum response is at the anode 

 side in sea-water, whether acid or alkaline. The tentacles and manubrium turn and point 

 toward the cathode. The tentacles may be caused to contract slowly and irregularly in a con- 

 stant current. They contract when the current is made and relax when it is broken. 



Loeb, 1906, finds that the magnesium of the sea-water serves to relax the muscles of the 

 bell, stomach, and tentacles of Pol\r>rcliis; and that the remaining salts of sea-water produce 

 a state of contraction, so that it we place the medusa in any solution resembling sea-water, 

 but lacking magnesium, pulsation is impossible and the tentacles and stomach are contracted. 

 If we add magnesium, however, pulsation is resumed, but this effect of magnesium can be 

 inhibited by addition of an equivalent amount of calcium or potassium. 



The isolated center of the bell will not beat in sea-water or in a sugar solution, but 

 beats commence in these solutions if we add calcium, strontium, or barium chlorides. No 



beats occur, however, if we add mag- 

 nesium chloride. The isolated center 

 will beat for 3 to 4 hours in any decalci- 

 fying salts, such as oxalates, fluorides, 

 oleates, citrates, etc. Acids cause the 

 center to beat, while alkalies inhibit 

 such beats. 



The center does not beat until some 

 hours after being placed in NaCl; but 

 then rhythmical pulsations set in and 

 may last 2 or 3 days. But pulsation 

 may be at once produced in NaCl by 

 adding salts which precipitate calcium, 

 such as sodium citrate, tartrate, oroxa- 

 late. A trace of HC1 or CO 2 added to 

 NaCl will also cause beats, as will pure 

 solutions of CaCl 2 , BaG 2 , or SnCl 2 . 

 Beats are inhibited more by !Mg than 

 by Ca. We have thus the \ anomaly 

 that contractions occur in an excess or 

 a deficiency of Ca. 



Maccallum, 1907, finds that solutions of cascara sagrada, rhubarb, aloin,podophyllin,and 

 colocynth produce temporary pulsations in the isolated center of Polyorehis. 



Polyorchis minuta Murbach and Shearer. 



Polyorchis minula, MURBACH AND SHEARER, 1903, Proc. Zool. Soc. London, vol. z, p. 174, plate 19, fig. 3; plate 22, fig. i; 1902, 

 Annals and Mag. Nat. Hist., ser. 7, vol. 9, p. 72. 



Bell 15 mm. high, 12 mm. broad. Truncated, oval, with thick walls; only 9 mm. wide at 

 velar margin. There are 55 or more tentacles. Yellow ocelli on outer sides of tentacle bases 

 on elevations. 4 narrow radial-canals with short, lateral diverticula. Stomach mounted on a 

 long peduncle extending to level of velar opening. 4 crenated lips. Gonads long, finger-shaped, 

 arising from the 4 radial-canals near base of peduncle. 



Gonads and tentacles pale yellow in preserved specimens, other parts colorless. 



Found in Puget Sound, British Columbia. 



Genus SPIROCODON Haeckel, 1880. 



SfirocoJon, HAF.CKEL, 1880, Syst. dcr Mcdusen, p. 636. 



Goneomeandrus, KIRKPATRKK, 1903, Annals and Mag. Nat. Hist., scr. 7, vol. 12, p. 616. 



The type species and only known form is Spirocodon saltatn\ ot the Inland Sea, Japan. 

 This was first described by Tilesius, 1818, as M,-Jus<i sallotrix. Haeckel, 1880, established 

 it as a type of the genus Spirocadon. 



Fit:, ill. Polyorchis ptnicillala, after Fewkes, in 

 American Naturalist. 



