ZOOLOGY AND BOTANY, MICnOSCOPY, ETC. 705 



primary axis of longitudinal growth ; they may be seen in Asterina or 

 Pluteus paradoxus ; they are probably a good deal modified in the turri- 

 forra bodies of pedate Holothurians, but this is a point which requires 

 further investigation. Notwithstanding the various slight difierences 

 which obtain in the hard structures the development, histology, and mor- 

 phology of the calcareous bodies show a union and resemblance which 

 help to mark off the Echinodermata from other divisions of the animal 

 kingdom. 



Coelenterata. 



Stinging-cells.* — Dr. K. v. Lendenfeld gives a useful summary of 

 researches by himself and many others on the structure and function of 

 stinging-cells. His account is useful both as an historical review and 

 as a systematic summary of what is definitely established with respect 

 to these elements. In regard to the mechanism of discharge, he sums up as 

 follows: — (a) Hamann's stalk is a support without any active role in the 

 discharge ; (6) the granular basal process is a nerve ; (c) the protoplasmic 

 mantle is contractile, and by its contraction the capsule, open superiorly, 

 is compressed and the thread protruded ; (ci) the cnidoblast admits of 

 the discharge of the nematocyst in this way that a pressure on the apex 

 from without is transmitted to the plasmic mantle of the cnidoblast and 

 occasions its contraction; (e) this direct reflex action may, however, be 

 inhibited by a voluntary nervous stimulus, so that even when the cnidocil 

 is touched the animal may prevent any explosion. 



Formation of fresh stalks in Tubularia.f — Dr. P. Mayer expresses the 

 opinion that what Herr Klaatsch has lately taken for the formation of fresh 

 stalks in Tuhularia are artificial products, and he thinks an examination of his 

 figures will show this to be the case ; we have here an example of the danger 

 of trusting solely to preserved material. 



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

 of about 18 inches in diameter when alive, which was taken in New Haven 

 harbour. As it appears to belong to the acraspedote family Pilemidse, it 

 may be called Nectopilema (verrilli) ; it appears to be most closely allied to 

 Pilema and Bhopilema, though differing from them in various particulars ; 

 it appears to connect the second division of the Pilemidfe — the Eupilemidae — 

 with the third or Stomolophidae, and its generic characters may be given 

 thus : — Six velar lappets in each octant; no tentacles ; sixteen scapulettes ; 

 eight oral arms with numerous gelatinous filiform appendages. These last 

 vary in size and length ; the term scapulettes is the English of Hackel's 

 " Scapuletten " and appears to be a preferable term to the more frequently 

 used " leaf-like appendages." 



Anatomy and Histology of Veretillum.§ — Dr. A. Korotneff finds that 

 the polyps of Verelillum have a very complex structure, there being a 

 diffeientiated nervous system and special cell-elements which cause the 

 extraordinary phosphorescence of the animal. In the cone the ectoderm 

 consists of epithelium, a differentiated musculature, and a nervous system 

 closely connected with the luminous cells. The epithelial cells are much 

 elongated and are continued into fine filaments, which pass transversely 

 through the musculature, and there are also spindle-shaped sensitive cells 

 which are drawn out into fine filaments. The muscular layer consists of 

 fine filaments in which are independent cell-bodies. Between the epithelial 



* Biol. Centralbl., vii. (1887) pp. 225-32. f Zool. Anzeig., x. (1887) p. 365. 



t Amer. Jouin. Sci., xxxiii. (1887) pp. 119-25 (1 pi.). 

 § Zool. Anzeig., x. (1887) pp. 387-90. 

 1887. 3 E 



