410 SUMMARY OF CUllRENT RESEARCHES RELATING TO 



and small, \vhicli bad obviously been swallowed. It is not understood wby 

 tbe Hydra does not discharge nematocysts at tbem, or wby tbe cysts tbem- 

 selves do not explode in tbe interior of tbe jDarasite. 



Stinging Cells.*— M. M. Bedot bas studied tbe structure and develop" 

 ment of tbe stinging-cells in Velellidae and Pbysalid^, He notes the 

 importance of confining tbe term cnidoblast to tbe cell wbicb gives rise to 

 tbe nematocyst or bomogeneoiis cajisnle inclosing tbe filament. In Velel- 

 lidfe four kinds of cnidoblasts are described — small and large, eitber witb 

 or witbout stalk. Tbe large cnidoblasts inclose large oval nematocysts 

 witb a bandle, and tbe filament rolled very regularly witbin tbe capsule, 

 wbile tbe small nematocysts in tbe small cnidoblasts are more elongated, 

 bave no bandle, and tbe filament irregularly disposed. In Pbysalidfe two 

 kinds are distinguisbed, diilering in lengtb of stalk and size of nematocyst. 



After noting tbe various modes of distribution and arrangement, tbe 

 autbor proceeds to give an account of tbeir development. Before tbe 

 stinging-pad is formed, a section of a tentacle exhibits among tbe ectoderm 

 cells certain cnidoblasts witb nematocysts in process of formation. Tbe 

 ectoderm thickens at two opposite jjoints. The developing cnidoblasts 

 come to tbe surface, but remain attached to the supporting mesoderm layer. 

 Tbe lengthening of tbe stalks of the cnidoblasts is not tbe cause, but the 

 effect of the formation of tbe pad. The formation of tbe gelatinous tissue 

 of tbe tentacles is also described. To follow tbe development of tbe 

 nematocysts, a piece of the central organ should be separated. The first 

 trace of the appearance of tbe nematocyst in the simple cnidoblast is tbe 

 formation of a vacuole wbicb grows in the protoplasm. From tbe margin 

 of tbe vacuole a little bud grows into tbe transparent contents. This is 

 the nematoblast which gives rise to tbe stinging filament. In Pbysalids 

 this rudiment increases as a pear-shaped bud, a canal ai^pears in tbe stalk 

 and extends into the swollen portion, the protoplasm condenses round tbe 

 canal and forms a wall. The envelope of tbe nematocyst is formed by tbe 

 transparent substance which fills the primitive vacuole. In both Pbysalids 

 and Velellids two nematocysts may be formed witbin a cnidoblast. In 

 Velellids the development is complicated by tbe presence of tbe bandle of 

 the filament. The nematoblast appears as a miniite sphere. Opposite the 

 stalk a prolongation grows out, rej^resenting the filament. The sphere 

 itself forms tbe first portion of tbe bandle, while a second spherule near 

 tbe filament forms tbe other portion of the handle and books. 



New Rhizostomatous Medusa.f — Mr. J. W. Fewkes describes a new 

 medusa, the only non-tentaculated member of the grouj) known, as yet, on 

 the Atlantic coast of North America, and be gives it the name Nectopilema 

 Verrilli. 



Owing to tbe damaged condition in wbicb it was found, only an im- 

 perfect description is possible ; and only tbe margin of the umbella and 

 oral arms are touched upon. 



Tlie new genus belongs to Hackel's family Pilemidaj, and probably to 

 tbe sub-family Eupilemida*. Its nearest allies appear to be Pilema and 

 Bhopilema; and it serves to connect the sub-families Eupilemidae and 

 Stomolopbidfe. 



New genus of Stylasteridae.J— Mr. R. Kirkpatrick describes a new 

 Stylasterid from Mauritius, for wbicb be proposes the name oi Phalangopora 

 regularis g. et sp. n. ; it is allied to Errina, but differs in having tbe gastro- 



* Rec. Zool. Suisse, iv. (1886) pp. 51-70 (2 pis.). 



t Amer. Jouru. Sci , xxxiii. (1887) pp. lHJ-2.) (1 pi.). 



X AuQ. and Mag. Nat. Hist., xix. (1887) pp. 212-4 (1 pi.). 



