576 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



So far the original paper : — in the new appendix the author endeavours to 

 show that the excretory organs of Vertebrates and Invertebrates have 

 developed along parallel lines, and fall into the following scheme : — 

 (1) The decentralised method, exemplified best in Platodes where there 

 is neither blood-circulation nor body-cavity, and excretion is effected by 

 canalisation of the organism. To this group, where the excretory organs 

 are protonephridia, belong also Endoproctous Bryozoa, Rotatoria, and 

 Annelid and Molluscan larvae. (2) Organisms with a circulatory system 

 and a space or spaces in which excretory products accumulate, have 

 metanephridia, or open tubes communicating on the one hand with the 

 exterior, and the other with the coelom. Such are Annelids, Molluscs, 

 and the embryos of Vertebrates. (3) Finally the nephridial tubes them- 

 selves take part in the excretory process, and as their walls become spe- 

 cialised and vascularised, the coelom loses its excretory significance and 

 diminishes in importance, though portions of it may become shut off 

 with the nephridia. Suggested in Annelids and Molluscs, this is most 

 distinct in Arthropods and Vertebrates, though accomplished according 

 to different plans in the two groups. This scheme is not supposed to 

 have phylogenetic value, the author believing that coelom and nephridia 

 may have originated independently in the different groups of the 

 Metazoa. 



y. G-astropoda. 



Pacific Opisthobranchs.* — Dr. E. Bergh gives an account of the 

 collection made by Prof. Schauinsland (1896-7), including Pleuro- 

 brancltsea novse-zelandise, Pleurobranckus aurantiacus, Chelidonura hirun- 

 dinina (A. and G.) var. clegans Bgh. sp. n. ?, Archidoris nyctea sp. n., 

 Molidiella drusilla sp. n., Mo. fausiina sp. n., and Samla annuligera 

 g. et sp. n. 



The last-named has the elongated lank form of all the Flabellinids, 

 beautiful perfoliate rhinophoria, a rounded anterior margin to the foot, a 

 triseriate radula, with a denticulate anterior margin to the lateral teeth, 

 and an unarmed penis. 



Arthropoda. 



o. Insecta. 



Development of Hydrophilus.f — Paul Deegener has investigated 

 the development of the mouth appendages and of the alimentary canal 

 in this form, the former especially with the view of determining the 

 accuracy of Meinert's views as to the differences between the appendages 

 of Coleoptera, Neuroptera, Hymenoptera, and Lepidoptera on the one 

 hand, and those of the Orthoptera on the other. He finds that the 

 sequence of the appendages in Coleoptera is identical with that in 

 Orthoptera, and that the labrum is completely homologous in the two 

 orders. The labrum in Coleoptera is not an appendage belonging to an 

 intercalary segment, as Meinert supposed. In regard to the origin of 

 the epithelium of the mid-gut, he finds that it arises from two anterior 

 and two posterior ventro-lateral ectodermal lamellae, which grow out 

 from fore- and hind-gut respectively, and, meeting in the mid-ventral 

 and mid-dorsal lines, constitute the mid-gut. The mid-gut is re-formed 



* Zool. Jahrb. (Abth. Syst.). xiii. (1900) pp. 207-46 (3 pis.), 

 t Zeitschr. wiss. Zool., lxviii. (1900) pp. 113-68 (3 pis.). 



