GO SUJMMARY OF CURRENT RESEARCHES RELATING TO 



Skeleton of Stromatoporoids.* — Yvonne Dehorne finds that the 

 minute structure of the skeleton of these extinct Hydrozoa is apt to lead 

 to fallacious conclusions. Thus that of the typical Actinostromaria 

 stellata is like that described by Ogilvie in the Madrepore Pontes in- 

 crustans. The zooecia of some Polyzoa show a similar structure. The 

 minute structure of the wall depends greatly on the mode of fossilization 

 and on subsequent transformations of this. Definition must depend 

 rather on the individualization of the zooids, on the mode of arrange- 

 ment, and on the growth of the whole colony, which permits of a recon- 

 struction of the aspect of the living hydrorhizal surfaces. 



Coppinia of Grammaria abietina.f — HjalmarBroch has studied in 

 this hydroid the aggregates of gonangia ^hich are known as coppinia. 

 The formation begins with the appearance of secondary stolons, which 

 form a feltwork over the primary twigs and give off the tubes and 

 gonothecse of the coppinia. The primary and secondary stolons are 

 united by numerous anastomoses. Into the coppinia the hydrothecs also 

 project, but they grow so that the oral apertures project beyond the felt- 

 work. After the reproduction is completed the secondary parts of the 

 coppinia are discarded, and the elongated hydrothec® are left for a time 

 conspicuously projecting. 



An account is given of the stinging-cells of the protective polyp. In 

 the lumen of the protective polyp traces of ova were sometimes found, 

 and these were traced through the stolons to the nutritive polyps. It 

 seems that the latter may devour liberated ova — a danger at the very 

 threshold of life. The author discusses the migration of the young ova 

 from the ectoderm of the primary and secondary stolons to the gonangia. 

 They may move in the endoderm as well as in the ectoderm in amoeboid 

 fashion, and they readily penetrate the middle lamella. The reproduc- 

 tive individuals show sex-dimorphism. The male gonophores are crypto- 

 medusoid in structure, the female heteromedusoid. 



Porifera. 



Chessman Spicule of Latrunculia.| — Arthur Dendy discusses the 

 development of the " discorhabd " of Latrunculia bocagei and L. apicalis. 

 In the former species it consists Of a straight, stout shaft, expanded at 

 the lower end to form a knob-like base (the " manubrium ") ornamented 

 with two circles of short spines. A little beyond the middle of the 

 shaft there is a whorl of three flattened lobes with denticulate or crenate 

 margins, followed after a short interval by a similar whorl, and then, 

 after another short interval, by a third whorl which differs from the 

 other two in not being subdivided into three lobes. Immediately after 

 the third whorl comes the broad, hemispherical apex, provided with a 

 number of short, capitate spines, and forming a sort of crown. Tlie 

 whorls may be called median, subsidiary, and apical. The length or 

 height of the fully-grown spicule is about 0'07 mm. 



In L. apkalis the spicule is continued beyond the apex into a slender 



* Comptes Rendus, clxv. (1917) pp. Vffl-G. 



t K. NorskeVidensk. Selskabs. Skrifter,1916,No. 1, pp. 1-16 (2 pis. and 3 fig.^.). 



: Journ. Quekett Micr. Club, liii. (1917) pp. 1-16 (3 pie.). 



