630 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and is not in itself a functional nematocyst battery. There is a well- 

 developed double nerve-ring at the base of the velum, similar in most 

 respects to that of Limnocodium and of other medusoids. 



The manubrium is undoubtedly functional as a digestive organ. 

 The gland-cells and digestive cells are restricted to the more proximal 

 regions, the oral endoderm being characterized by the presence of an 

 unusually large number of mucus-secreting goblet-cells. The develop- 

 ment of the medusa-buds presents several interesting features, some of 

 which are undoubtedly primitive. 



Structure and Affinities of Thyroscyphus.* — A. Kiihn gives for 

 the first time an account of the minute structure of this Hydrozoon. He 

 discusses its affinities and establishes a new species, Thyroscyphus gracilis. 

 By the nature of the periderm-sheath and of the hydranth body it is 

 separated from the Campanularids and Campanulinids. It should 

 probably be ranked near the base of the Sertularid stock. 



Porifera. 



Degenerative Changes in Sponges.f — 0. Maas has experimented 

 with Sycandra raphanus, Leucosolenia Heberkiihnii and Chondrosia reni- 

 formis, observing the results of lack of lime salts, lack of food, and so 

 on. Processes of involution set in, comparable to gemmule-formation, 

 and these are followed after a pause by revivification. The sponge-body 

 becomes simplified and shows its essentially diploblastic (not triploblastic) 

 constitution. In the resting stage there are internal granular cells and 

 external covering cells. The internal cells are due to the activity of 

 phagocytes which absorb the gastral cells and other elements. In the 

 Calcarea these phagocytes are modified porocytes ; in the Dernospongia? 

 they are migratory " cellules spheruleuses " of the middle stratum. One 

 of the interesting general results is the indirect confirmation of the view 

 that sponges are fundamentally diploblastic. 



Merlia.J — R. Kirkpatrick gives an account of the remarkable sponge 

 known as Merlia normani, found by Canon Norman and afterwards by 

 the author in 60 to 90 fathoms off Porto Santo and Madeira. It is a 

 vermilion-coloured encrusting monaxonellid sponge belonging to a new 

 sub-family — Merlinge — of the Haploscleridre. Large granular amcebo- 

 cytes (calcocytes) have constructed a basal calcareous skeleton, formed 

 of vertical tubes divided up by horizontal tabulae. The tubes are built 

 up of columns, each with three vertical wings which unite with wings of 

 neighbouring columns to form tubes. This mode of construction was 

 probably primarily determined by the disposition of the branches of the 

 rhoanosome, which led to the deposition of amcebocytes at the points of 

 bifurcation of the lines of flagellated chambers. 



Apparently the calcocytes become wholly transformed into lumps, 

 connles, or flakes. The calcareous skeleton shows certain resemblances, 

 especially at the surface, to certain Palreozoic fossils, classed among 



* Zool. Jahrb., xxxi. (1911) pp. 25-38 (1 pi. and 3 figs.). 



t Festschrift R. Hertwig, iii. (1910) pp. 93-130 (3 pla. and 2 figs.). 



X Quart. Journ. Micr. Sci.,M. (1911) pp. 657-702 (7 pis. and 5 figs.). 



