40 SUMMARY OF CXmRENT RESEARCHES RELATING TO 



sank to the bottom of the coll. These were, so far as could bo 

 ascertained, poisoned, and this was probably owing to the free 

 sulphide of hydrogen evolved by the putrescent sewage. From his 

 observations the author is led to infer that rotifers will live and 

 multiply on a very scanty supply of organic matter, provided only 

 that the water is fairly well oxygenated. Attention is also called to 

 the greatly diminished or no longer developed eye, due, no doubt, to 

 the withdrawal of the stimulus of light, the rotifers being nearly 

 always kept in the dark. 



Organisms in Ice.* — Prof. Leidy relates that he had placed in 

 his hands, for examination, a vial of water obtained from melting ice 

 which is used for cooling drinking-water. From time to time, among 

 some sediment taken from a water-cooler, his infoi-mant had observed 

 what ho supposed to be living worms, which ho suspected were 

 introduced with the water into the cooler, and not with the ice. 

 Upon melting some of the ice alone, the worms were still observed, 

 and the water submitted for examination was some that was thus 

 obtained. Prof. Leidy was surprised to find a number of worms 

 among some flocculent sediment, mainly consisting of vegetal hairs 

 and other debris. Besides the worms, there were also immature 

 Anguillulce, and a number of Rotifer vulgaris, all living. It would 

 appear that these animals had all been contained in the ice, and had 

 been liberated on melting. It was an unexpected source of con- 

 tamination of drinking-water, that Prof. Leidy had previously 

 supposed to be very improbable. 



The worms were probably an undescribed species of Lumhriculus. 

 Several dead worms swarmed in the interior with large, ovate, beaked, 

 ciliated infusorians measuring from 0*05 to 0*06 mm. long by 0-04 

 to 0*48 mm. broad. 



Mollusca. 



Integument of Cephalopods.t — In bis second J essay on this 

 subject P. Girod deals with the suckers of Cephalopods; his observa- 

 tions were made on Octopus vulgaris and Sejjia officinalis, which, as is 

 well known, difi'er from one another by the fact that in the latter, as 

 in all Decapods, the suckers are stalked and not sessile as in Octopus ; 

 with this difference other secondary points are associated. In Sepia 

 the cavity of the sucker is single and not, as in Octopus, provided 

 with an infundibular antechamber ; there is a horny ring with 

 terminal teeth which is absent in Octopus, and there is also a pro- 

 jecting piston-like apparatus. 



The differences in form are associated also with differences in 

 texture, for while the Octopod has an clastic cup constricted in its 

 middle by a contractile ring, which is the seat of insertion of 

 extrinsic dilatator muscles, and is able to modify considerably the 

 extent of its internal cavity, the Decapod sucker is much less mobile, 



* Proc. Acad. Nat. Sci. Pliilad., 1884, p. 260. 



t Arch. Zool. Exijcr. ct Gen., ii. (1884) pp. 379-401 (1 pi.). 



X For tbc first, see this Journal, iv. (1884) p. 36. 



