542 SUMMARY OF CURRENT RESEARCHES RELATING TO 



derm, as well as in the mesogloea, green bodies occur which give the 

 iodine test for starch and are apparently symbiotic Algae. These are 

 present in both the adults and larvas, and enable both to live in shallow 

 lagoous in water which would be too poor in oxygen for most marine 

 animals. Developing eggs were not met with, but the abundant scyphi- 

 stoma larvas were found to be multiplying rapidly by budding. The 

 buds when set free resemble planulas, except that they possess a well- 

 defined mesogloea and four septal muscles. The mouth arises at the 

 former point of attachment, while the distal end of the bud becomes 

 the stem. There is no evidence of any invagination of ectoderm in the 

 formation of the mouth, both the gullet and the gastric pouches being 

 lined with endoderm. Generally, it may be said that there is no 

 evidence of the existence of an anthozoon stage in the larva? produced 

 by budding. The scyphistoma becomes metamorphosed into the young 

 medusa, but a small basal segment remains which, after the setting free 

 of the medusa, develops into a perfect scyphistoma and repeats the 

 process. This basal segment is closely analogous to the planula-like 

 buds formed from the young scyphistoma. 



Movements of Medusae.* — J. von Uexkiill has studied Rhizostoma 

 pulmo in the living condition, in order to re-investigate the question of 

 the relation of the marginal bodies to the rhythmic contractions. He 

 finds that the marginal bodies are not centres presiding over the 

 rhythm ; they are nothing more than receptive organs for mechanical 

 stimuli. At every stroke they swing to and fro on their stalks, and 

 thus give rise to a stimulus which spreads over the nerves, reaches the 

 muscle-centre, and thus leads to the contraction of the muscles. The 

 first stroke, in a medusa which has been lying at rest, is due to a 

 spontaneous muscular contraction, and occurs equally in a specimen 

 from which the marginal bodies have been removed. 



Alcyonarians of the Gulf of Lyons, f — The late Prof. H. de Lacaze- 

 Duthiers had, as one of his last pieces of work, made a study of 

 Sympodium corallo'ides and Bolandia corallo'ides g. et sp. n. He con- 

 trasted the two forms, as regards zoanthodeme, sarcosome, spicules, 

 polypes, and so on, describing aud drawing in his characteristic fashion 

 with no hint of diminution of skill or loss of cunning. 



Protection of the Young in Actiniaria.J — 0. Carlgren describes the 

 various modes : — (1) The embryos may develop in the ccelenteric cavity ; 

 in the Arctic genera Urticina and Actinostola, they remain there till they 

 have several circles of tentacles. (2) The embryos may be attached to 

 the body-wall and develop there, (a) without there being brood- pouches 

 (Epiaciis prolifera), or (6) in special brood-cavities formed by invagi- 

 nations of the body-wall. These may be numerous and arranged in 

 longitudinal rows, and each may contain one young one or a few. 

 (Pseudophyllia arctica, Epiactis marsupialis sp. n., Epigonactis fecunda 

 and E. regidaris, Leiotealia spitzbergemis, Condylactis georgiana); or 

 there may be only a few (6) large brood-cavities, each with numerous 

 embryos (Marsupifer valdivise sp. n.). 



* MT. Zool. Stat. Neapel, xiv. (1901) pp. 620-6. 



t Arch. Zool. Exper., viii. (1900) pp. 353-462 (5 pis.). 



% Biol. Centralbl., xxi. (1901) pp. 468-84 (13 figs.). 



