228 SUMMARY OF CUREENT RESEARCHES RELATING TO 



superficial layers of the vesicle where they spread out into small 

 cones ; in rarer cases the rays do not reach the surface, and in others 

 they are wanting, when the central mass has an irregular spherical 

 form. Prof. Sabatier says that he has not been able to make out a 

 distinct relation between the form of this chromatic plexus and the 

 genesis of the vitelline corpuscles; but he concludes that the 

 nucleolus and the nuclear plexus are not composed of identical 

 substances, and that the latter, even when in a spherical condition, is 

 still distinguished from the nucleolus, which cannot, therefore, be 

 considered as an agglomeration of the substance of the plexus. 



Odontophore of Limngea.* — Dr. W. Dybowski, who has already 

 reported on the dentition of Ancyclus, Physa, AmpMpeplea, and 

 Planorhis, now gives the fifth type represented in the fresh-water 

 pulmonate gastropods — the formula is 1-19-15-15. The species 

 examined was L. stagnalis var. vulgaris; the radula is 4 mm. long, 

 and 2*2 mm. wide; there are from 100-102 rows. 



Notes on GymnosomatoTis Pteropoda.t — Dr. J. E. V. Boas, in 

 anticipation of his monograph on the Pteropoda, notes that d'Orbigny's 

 genus SpongiohrancTieea contained two species, S. elonjata and S. aus- 

 tralis, which are by no means allied ; the former is a Clione, the latter' 

 the type of a very well-marked genus, which is most closely allied to 

 Pneumodermon, and to Dexiohranchsea. The latter is a new genus 

 which difi'ers more from Pneumodermon than does Spang iohranchsea 

 and is characterized by its lateral gill, and by the complicated 

 sucking apparatus ; it contains four species, one of which was called 

 Pneumodermon ciliatum by Gegenbaur, while the others are new. 



The author recognizes six well-marked genera in the group of the 

 Gymnosomata ; these are Pneumodermon, Glione, Haplosyche, Gliopsis, 

 and the two already mentioned; the genus Cirrifer of Pfeffer is 

 founded on an injured Pneumodermon, and all the rest are either so 

 badly described as not to be recognizable, or are formed on species 

 which belong to one of the six recognized genera. 



MoUuscoida. 

 ^. Polyzoa. 



Fresh-water Polyzoa of Bohemia.^ — Herr J. Kafka gives an 

 account of the five species of fresh-water Polyzoa already known from 

 Bohemia, and describes eight others, amongst which Plumatella 

 hyalina and P. lopJiopsidea are new. The first of them is allied to 

 P. vesicularis by the transparency of its tubules, which arise radially 

 from a centre, and branch dichotomously at some distance from it ; 

 the second has at first some resemblance to LopJiopus, but the gela- 

 tinous investing mass is an ectoblast-membrane, while the organiza- 

 tion of the cells and polypides is that of Plumatella. Contrary to 

 what ordinarily obtains on the continent of Europe, and like what 

 is seen in England, Fredericella sultana is common in Bohemian 



* Bull. Soc. Impe'r. Moscou, Ix. (1885) pp. 256-62 (1 pi.), 



f Zool. Anzeig., viii. (1885) pp. 687-91. 



I SB. K. Bohm. Gesell. Wis.?. Ping, 1884 (1885) pp. 229-40 (1 pi ) 



