88 SUMMARY OF CUREENT RESEARCHES RELATING TO 



third series of outgrowths, whicli do not appear till the embryo is 

 about to leave the egg. 



The effereut blood-vessel is early developed, occupies almost the 

 centre of the organ, and is contained in the base of the layers and of 

 the branchial gland. The efferent vessel is developed on the crest of 

 the gill and on the outer edge of the layers just described ; it has the 

 same undulating course as the parts which carry it, and is, at the base 

 of the gill, directly continuous with the auricle of its own side. 



Further Eesearches on Nudibranchs.* — E. Bergh prints an im- 

 portant paper, illustrated by five plates, as a supplement to his mono- 

 graph of the family of which Polycera Cuvier is the typical genus. 



After a number of general notes on species and genera, among 

 which is the description of Ohola, a new genus collected by the 

 ' Challenger,' at Trapura, in the South Seas, the author considers the 

 Dorididse in general, with their divisions and probable phylogeny. 

 The genus Heterodoris of Verrill and Emerson is considered as pro- 

 bably belonging to a different family. The Dorididse are separated 

 into two very well marked groups by the possession of a single large 

 retractile crown of gills, or of numerous retractile branchia : Crypto- 

 branchiata and Phanerobranchiata respectively. The latter, connected 

 with the typical Dorididse through Staurodoris, diverge in two lines, 

 of which the more ancient forms are Notodoris and Akiodoris. The 

 former culminates in Placamophoriis, with Ohola as a lateral branchlet. 

 The latter passes through Acanthodoris, Goniodoris, &c., towards Ancula 

 and Drepmiia. 



The phanerobranchiate, non-suctorial Dorididse form the Poly- 

 ceradse (better Polyceratidae) of Bergh, and the suctorial forms his 

 GoniodorididsB. A synopsis of the genera and species of these groups 

 is given. They inhabit all seas, but are largest and most beautiful 

 in the warmer regions. 



runctions of the Eenal Sac of Heteropoda.^ — L. Joliet was able 

 to notice on a living PhyUirJioe that the renal sac was folded, and that 

 it opened slowly ; this movement was clearly due to the action of the 

 cilia of the pericardiac orifice. When the sac was full its own orifice 

 opened slowly, remained visible for some seconds, and then dis- 

 appeared. In the Firolidse there is a system of external muscles, by 

 means of which the renal organ may perform a true diastole. The 

 author addressed himself to the problem whether the water taken in 

 this diastole entered into the pericardium, or whether, on the contrary, 

 water passed out from that cavity. The results of his observations of 

 living forms were to convince him that the water which bathes the 

 renal cavity does not enter into the pericardium, and that it is the 

 function of the renal sac to extract liquid from the blood, to expel it 

 to the exterior, but not to draw water from without to pass it into the 

 blood. In fine, we must agree with the teaching of Lacaze-Duthiers, 

 that an organ whose principal function is to secrete the products of 



* Verb. Zool. Bot. Gesellsch. Wien, 1883. Cf. Science, ii. (1883) p. 748. 

 t Comptes Rendus, scvii. (.1883) pp. 1078-81. 



