200 SUMMARY OF CURRENT RESEARCHES RELATING TO 



as forty new species in the collections dredged in the Gulf of Mexico 

 and the Caribbean Sea. Nearly all were obtained from depths less 

 than 200 fathoms ; new and very singular types were obtained on the 

 three occasions when Comatulaa were brought up from more than 

 300 fathoms. As very similar conclusions are to be drawn from the 

 ' Challenger ' collection, it seems that Comatulfe are essentially 

 inhabitants of shallow water. When we compare the two collections 

 it is interesting to see how they supplement one another. Ten-armed 

 forms abound in the Caribbean, while in the eastern seas the majority 

 have the rays always dividing, in some cases as many as seven 

 times. The characters of several little-known species are discussed, 

 and Antedon spinifera n. sp., and Actinometra puhhella Pourtales are 

 described in detail. Attention is again directed by the author to the 

 characters which distinguish the genera Antedon ami Actinometra, and 

 these are usefully summarized in a table. 



Two Pentacrinoid forms were found entangled in the arm of 

 Act, meridionalis, and are presumably the young of that species ; if 

 so, they are probably the first Pentacrinoid Actinometrse that have 

 been observed : a study of these specimens and of young Anted ons 

 leads to the belief that the late appearance, as a whole, of the basal 

 pinnules is a " marked developmental character among the Comatulae." 

 This is of interest in connection with Mr. Carpenter's account of a 

 new genus Atelecrinus, in which the basal circlet is complete in the 

 adult as it is in some Pentacrini, and the earlier stages of Pentacrinoid 

 larvse. In the characters of its calyx this new genus retains per- 

 manently larval characters ; so, too, there is an absence of pinnules 

 from the lower part of the arm. Ant. cuhensis with the new species 

 A. balanoides will belong to this genus. 



Coelenterata. 



Characters of Stinging-cells of Coelenterata.* — Dr. C, Chun 

 recalls the fact that late investigations have directed attention to 

 the nature of the processes which connect the stinging-cell with 

 the supporting lamella (" mesoderm ") ; Claus has regarded them as 

 muscular fibres, and the brothers Hertwig as nervous structures. 

 If we examine their mode of termination we find that they may 

 or may not pass into the ectodermal longitudinal muscles of the 

 tentacles. Observations tending to the conclusion that the processes 

 in question are representatives of muscles are confirmed by the exami- 

 nation of Physalia, for in this Siphonophore it is to be observed that 

 hundreds of muscular lamellte arise, with extraordinary regularity, from 

 the muscular band which passes to some of the filaments ; the vessel 

 running through the middle of the band gives off, under each battery 

 of stinging-cells, a widening branch, the endodermal cells of which 

 are remarkably increased in size beneath the battery. In other 

 words, we find in Physalia a mesoderm well developed and traversed 

 by cellular elements. The rounded nettle-capsules of each battery 

 may be small or superficial, or larger and deeper. The stalks of the 



* Zool. Anzeig., iv. (1881) pp. 646-50. 



