ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 663 



crinus, the oral plates of the larva become resorbed as maturity is 

 approached. In Thaumatocrinus, however, they are retained, as in 

 Syocrinns, Rhizocrinus, and Holopiis, representatives of three diiierent 

 families of Neocrinoids. 



3. There is no Neocrinoid, either stalked or free, in which the 

 primary radials remain permanently separated as they are in Tliau- 

 matocrinus, and for a short time after their first appearance in the 

 larva of ordinary Crinoids. The only Paleeocrinoids presenting this 

 feature are certain of the Bhodocrinidce, e. g. Beteocrimis, Ehodocrinus, 

 TJiylacocriniis, &c. In the two latter and in the other genera which 

 have been grouped together with them into the section Ehodocrinites 

 there is a single interradial intervening between every two radials, 

 and resting on a basal just as in Thaumatocrinus. But in the Lower 

 Silurian Beteocrinus the interradial areas contain a large number of 

 minute pieces of iiTegular form and arrangement. 



4. It is only, however, in Beteocrinus and in the allit-d genus 

 Xenocrinus Miller, which is also of Lower Silurian age, that an anal 

 appendage similar to that of Thaumatocrinus is to be met with. 



Of the four distinguishing characters of Thaumatocrinus, therefore, 

 one appears in one or perhaps in two genera of Comatulce ; another is 

 not to be met with in any Gomatula, though occurring in certain 

 stalked Crinoids ; while the two remaining characters are limited to 

 one family of the Palteocrinoids, one of them being peculiar to one or 

 at most two genera which are confined to the Lower Silui'ian rocks. 

 Their appearance in such a specialized type as a recent Comatula is 

 therefore all the more striking. 



Coelenterata. 



Coelenterates of the Southern Seas.* — E. v. Lendenfeld in his 

 third communication deals with offensive polyps and stinging-cells. 

 Taking the former as they are found in the Plumularidas he finds that 

 they are referable to three primary groups — offensive animals with 

 stinging-capsules, offensive animals with attacking-cells, and offensive 

 animals with both. The first of these are described, and it is pointed 

 out that if we start from a Protohydra with hollow tentacles we find 

 that, as it is gradually converted into an offensive polyp of a Plumu- 

 larid, there is a gradual compression of the gastric cavity. The 

 tentacles first become solid, and then the gastric walls fuse ; the cen- 

 tralization of the gastric cavity in the person is followed by centrali- 

 zation in the colony. 



The forms of the second class are principally found in those 

 nematophores of the species of Aglaophenia which lie in front of the 

 nutrient persons. Instead of urticating-capsules they are provided 

 with attacking-granules which absolutely correspond in structure to 

 the similar elements in the " fishing-lines " of the Ctenophora. The 

 polyps of the third class have as yet only been observed in the genus 

 Aglaophenia ; the nematophores which contain this kind of " macho- 

 polyp," have, in addition to the circular orifice at their end, an oval 



* Zeitschr. f. Wiss. Zool., xxxviii. (1883) pp. 355-71 (1 pi.)- 



