680 SUMMARY OF CUREENT RESEARCHES RELATING TO 



Structure and Classification of Echiurus chilensis.* — Philipp 

 Seitz gives a detailed account of the structure of this form, and as a 

 result of his investigation has established for it along with Echiurus 

 tmicinctus a new genus Urechis. The chief characteristic upon which 

 this arrangement is based is the number of the segmental organs. 

 Urechis chilensis has three pairs, and U. unicinctus two pairs. U. chi- 

 lensis, though the more recently known, is to be regarded as the type, 

 since for this species some characters are known which hitherto have 

 not been demonstrated for U. imicinctus. The generic characters are 

 fully tabulated in the memoir. 



Pigment of Bonellia.f — R. Dubois extracted the pigment fluoro- 

 chlorobonelline from the integument of Bonellia viridis by means of 

 alcohol. It was experimented with by exposure to Hght. Violet and 

 blue light did not sensibly destroy the green matter nor diminish its 

 dichroism (nor probably its fluorescence). White light decolorises it. 

 Green, yeUow, and red gave slight decoloration. Decoloration was 

 rapidly provoked by oxygenated water, but not by reducing agents. In 

 darkness the solution is not altered. It is regarded as probable, in 

 Bonellia, as in other green animals, that light increases cutaneous respira- 

 tion. Some experiments with Eulalia davigera are also described, in 

 which it was found in excess of light to emit a rose pigment, probably 

 as a defence from an excess of oxidation. 



Chsetognatha.l — R. T. Giinther gives an account of the Chasto- 

 gnatha with a view to demonstrating that, as far as our present know- 

 ledge goes, there are more numerous and cogent reasons for allying 

 them with the MoUusca than with any other group, and that no organ 

 of importance has been described in Chaetognath anatomy which has 

 not been closely paralleled by similar and indeed homologous organs 

 among the Mollusca. The morphological characters he emphasizes 

 in support of his contention are mainly these. The Chsetognatha 

 present the original bilateral symmetry of the Mollusca in its most 

 perfect form. They resemble many Molluscs of undoubtedly primitive 

 type in the absence of apparent segmentation. There is no evidence of 

 a radula either in the Chsetognatha or their ancestors. The buccal 

 armature is like that of many Molluscs. The nervous system is of the 

 Molluscan type. The genital cells grow within a follicular epithelium, 

 and upon stalks. The two pairs of openings from the perigonadial 

 cavity to the exterior are believed to be the homologues of two pairs of 

 ducts in primitive Mollusca. The "hood" may be regarded as homo- 

 logous with the Cephalopod circumoral " foot," and the preoral ciliated 

 ring with the " velum." The Chaetognatha, the author claims, may 

 fairly be regarded as the living adult representatives of the phyletic stage 

 indicated by the veliger larva. A scheme of classification representing 

 this view is appended. 



* Zool. Jahrb., xxiv. (1907) pp. 322-56 (3 pis.). 



•t C.R. Soc. Biol. Paris, Ixii. (1907) pp. 654-5. 



t Quart. Journ. Micr. Sci., li. (1907) pp. 357-95 (10 figs.). 



