ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 55 



angle larger than 45°, there is no displacement of the lateral polyp, the 

 extirpated axial polyp regenerating as though it alone had been removed 

 by a transverse cut. When a lateral group of polyps is removed by a 

 longitudinal cut, it regenerates a new peduncle approximately at a right 

 angle to the cut surface, and approximately in the axis of the chief 

 lateral polyp of the group. The futuro of such pieces is unknown. 

 This is a case of heteromorphosis. 



Multicellular Sense-Organs in Syncoryne sarsii.* — E. Citron has 

 studied what Schulze describes as palpocils on ithe tentacles of this 

 hydrozoon, and finds that each consists of a group of (at least two) 

 sensory cells ending peripherally in a stiff pointed filament, and basally 

 in a nervous plasmic process. The adjacent covering cells of the ecto- 

 derm form a conical protection for the sensory group, and this is per- 

 forated by the projecting filament. 



Development of Gonothyraea loveni.f — J. Wulfert notes in a pre- 

 liminary communication the following points. The migratory primitive 

 sex-cells appear very early, soon after the fixing of the planula. They 

 arise from interstitial ectoderm cells, and migrate eventually to the 

 gonangia ; in older stocks there is a continuous procession. The form 

 and position of the ovum in the gonophore is variable. Two polar 

 bodies are given off. Fertilisation occurs in two ways (not mentioned), 

 and the cleavage is of two types connected by intermediate modes. A 

 cceloblastula is formed and the endoderm is established by multipolar 

 immigration. But in the second type of cleavage some cells are in- 

 ternal at about the 24-cell stage, so that cleavage and endoderm-forma- 

 tion cannot be rigidly separated. The segmentation-cavity is filled up 

 with endoderm cells, and the embryo becomes a solid planula. This 

 settles down, becomes a flat disc, and buds off a hydrocaulus from its 

 ■centre. 



Revision of Genus Sertularella.t — CI. Hartlaub has tried to put 

 this genus in order. There are about 90 species, mostly littoral, pre- 

 dominantly Arctic and Antarctic (47 sp.). There is great diversity 

 in bathymetrical distribution, e.g. S. tricusjpidata from 11 to 2438 metres, 

 and S. polyzonias from the shore to 500 metres. The specific tables 

 show that there is great variability in details. Two groups are recog-. 

 nised, — with a 3-valved operculum (tricusjriclata) and with a 4-valved 

 operculum (rugosa-polyzonias). These groups are also marked by dif- 

 ferences in the position and form of the gonothecae. 



Porifera. 



Gemmation of Tethya.§ — Dr. Otto Maas has studied the methods 

 of reproduction of this interesting sponge, which is not known to pro- 

 duce sexual elements. It periodically gives rise to buds, which are 

 liberated from the parent, and float away as young sponges, but the 

 exact origin of these has not hitherto been ascertained. Maas finds 

 that they do not arise from parthenogenetic ova, but nevertheless offer 



* Zool. Anzeig., xxiv. (1901) pp. 625-6. f Tom. cit., pp. G26-7. 



t Abb. Nat. Ver. Hamburg, xvi. (1901) 143 pp.. 6 pis., and 56 figs. See Zool. 

 Ceutralbl., viii. (1901) pp. 5b7-8. 



§ Zeitschr. wiss. Zool., lxx. (1901) pp. 263-8S (2 pis.). 



