332 SUMMARY OF CURRENT RESEARCHES RELATING TO 



peripheral ring of protoplasm, placed in the peripheral furrow. Of 

 these two connections the first is very transient, disappearing before the 

 four-cell stage, but the second persists. In the later divisions the seg- 

 mentation cavity becomes more complex, but always retains its primitive 

 character of a cleft in the protoplasm. In addition to the peripheral proto- 

 plasmic band which is undoubtedly primary, other secondary connections 

 of a less constant nature may also occur. 



Growth and Food-supply in Starfish.*— Mr. A. D. Mead has made 

 a series of observations on the rate of growth in Asterias forbesii, and 

 finds that it is extraordinarily rapid and extraordinarily variable. The 

 date when the larvae begin to " set " was noticed, and about a month 

 later minute specimens were obtained which were kept as nearly as 

 possible under natural conditions until November. It was found that 

 the rate of growth depended on one factor only — the supply of food ; 

 where this is abundant, the starfishes eat voraciously and grow rapidly ; 

 where it is scanty, growth is arrested, though the animals may remain 

 perfectly healthy. Again, a starfish does not become sexually mature 

 until it has attained a certain size, so that an abundant food-supply 

 hastens maturity, while an inadequate supply retards it. The growth 

 phenomena of the starfish are thus very different from those of a verte- 

 brate, where the relation between size and age is tolerably constant. A 

 practical corollary is that in observations on variation, size cannot be 

 taken as affording any index of age; this is probably true of other 

 invertebrates also. 



' Albatross ' Ophiuridae.f — C. F. Liitken and Th. Mortensen deal with 

 66 species, of which 53 are new, from the tropical regions of the eastern 

 Pacific. A new genus Gymnophiura is established near Ophioglypha ; 

 the central dorsal part of the disc is more or less naked. Four Atlantic 

 forms were found, and seven others are at least nearly related to 

 Atlantic species. The collection did not include a single viviparous 

 form. 



Studies on Synapta.J — Mr. H. L. Clark has studied Synapta tenuis 

 Ayres (= S. girardii Pourt. and apparently agreeing thoroughly with 

 the European S. inhserens), and S. roseola which is a very distinct 

 species. Both forms can be readily kept in aquaria with a deep bed of 

 sand for burrowing in. The reproductive period is in midsummer. The 

 anchors, which increase in size and number at the posterior end, support 

 the animal in its movements in the sand. 



Experiments showed that the " auditory vesicles " are not auditory, 

 but statocysts or " positional organs." The ciliated funnels are large 

 " lymph-stomata " and are excretory. Regeneration occurred only on 

 the excised head-portion including the mouth and fore-gut. 



Coelentera. 



North Atlantic Hydroida.§ — Kristine Bonnevie reports on the 

 collection of the Norwegian North Atlantic Expedition, which com- 



* Anier. Nat., xxxiv. (1900) pp. 17-23 (1 fig.). 



t Mem. Mus. Zool. Harvard, xxiii. (1890) 208 pp., 22 pis., 1 map. See Zool. 

 Centralbl., vii. (1900) p. 139. 



X U.S. Fish. Comm. Bull., 1899, pp. 21-31 (2 pis.). See Zool. Centralbl., vii. 

 (1900) p. 140. 



§ Norske Nordhavs-Expedition, xxvi. (1899) 104 pp., 8 pis., 3 figs., 1 map. 



