180 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The third type is that of Gopeus copeus {Ehrenbergi) and Eosphora 

 aurita, where the sac has two additional lobes, one on each side of the 

 central organ. 



The retro-cerebral organ, according to the author, is essentially 

 glandular, connected with the dorsal side of the brain, bifurcated in 

 front at least, opening outwards by two openings, and elaborating a 

 secretion which is capable of being stained in the living animal with 

 neutral red. 



In Notommata and similar forms it seems, from its close connection 

 with the brain and eye, to have adapted itself also to a sensory func- 

 tion, and to elaborate a new secretion in the form of minute opaque 

 granules. In Gopeus and Eosphora it has two additional lobes which 

 may contain similar granules. 



It will now be necessary to follow the ontogenetic and phylogenetic 

 development of this organ, to elucidate its supposed functions, and to 

 study the physical and chemical properties of its secretions. 



Northern Marine Rotifers.* — In Part X. of a work called " Nord- 

 isches Plankton," on the floating marine fauna and flora of the Northern 

 seas, R. Lauterborn has compiled ia useful list of all the known 

 Rotifers inhabiting the sea, altogether some >>0 species and varieties, 

 with figures of the marine Synchceta, Anuroza, and Notholca. 



Conochiloids, New Genus of Rotifers.f — S. Hlava has transferred 

 Gonochilus dossuaris (Hudson) and G. natans (Seligo) to this new genus 

 characterised mainly by the animals living singly, or very few together 

 in a gelatinous envelope, and possessing two large dorsal antennae. The 

 author then describes the minute structure of Conochiloides natans in 

 great detail, comparing at same time the different organs with those of 

 other Rotifers which have been studied in the same way. No new 

 features in the anatomy of Rotifers are brought out. 



Rotifera in Iceland.:}: — C. Wesenberg-Lund, in a study of the 

 plankton of the two Icelandic lakes, Thingvallavatn and Myvatn, from 

 samples collected for him at regular fortnightly intervals during a whole 

 year, records the following 1 1 species of Rotifers : Polyarthra platyptera, 

 Synchccta neglecta (should be oblonga), Ploesoma lenticulare, Asplanchna 

 priodonta, Anurcea acideata, A. cochlear is, Notholca longispina, N. striata, 

 Triarthra longispina, Brachionus pala, Gonochilus unicornis. The list of 

 species of both the lakes is almost identical, although Thingvallavatn is 

 situated in the south-western part of the island, is very deep and never 

 freezes, whilst Myvatn is situated in the northern part of the island, is 

 very shallow and is covered with ice from November to the end of May. 

 The highest summer temperature of the water is 11° and 12° C. respec- 

 tively. 



Echinoderma. 



Structure of Pentacrinus Decorus.§ — A. Reichensperger has been 

 fortunate enough to secure some good material from the " Blake " 

 collection, and has discovered some new facts. 



* Nordisches Plankton. X. Rotatorien, pp. 18-42. 



t Zeitschr. wiss. Zool., xviii. (1905) pp. 282-326 (2 pis.). 



X Proc. Roy. Soc. Victoria, xviii., n.s. (1905) pp. 16-19 (1 pi.). 



§ Zeitschr. wiss. Zool. lxxx. (1905) pp. 22-55 (3 pis. and 1 fig.). 



