ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 583 



true obstacle to fertilization. But the liquid is hurtful, as was seen by 

 the arrest of the spermatozoa in lots 2, 4 and 5, noted above. Ova of 

 the sea-urchin activated by butyric acid undergo cyclical changes in their 

 cytoplasm, which are repeated twice in the first fifty minutes of their 

 immersion in sea-water. At the beginning and end of each cycle the sub- 

 stance of the egg is permeable by a spermatozoon, which may complete 

 the work of the parthenogenecic agent. In the intervals the substance 

 of the egg is quite refractory, and the spermatozoa which are able to pass 

 into the perivitelline liquid die there. The intimate changes in the 

 egg are probably physical rather than chemical, and due to oxidations. 



The radiation always observed in the ova fifty to eighty minutes after 

 the beginning of activation do not hinder fertilization. In normal 

 fertilization the activation does not close its first cycle, because it is con- 

 tinued directly into the phenomena preparatory to cleavage. The primary 

 inhibition is definitive, and a belated polyspermy is impossible. Herlant 

 has observed that the efficacy of Loeb's method has two optima, which 

 correspond approximately to the two periods of ovum-receptivity which 

 Brachet's experiments have disclosed. 



Ccelentera. 



Notes on Anemones.* — Richard Elmhirst notes that anemones with 

 double disks may remain thus in captivity for years. A specimen of 

 Actinia equina with two complete disks, mouths and sets of tentacles 

 remained in the same state nearly four years. Another with two almost 

 complete disks became normal again. A normal specimen put into a 

 well-lit aquarium practically never closes its tentacles, but keeps them 

 hanging limply down. It became olivaceous and its young are olivaceous, 

 suiting the surroundings. One of the offspring divided across the base 

 in about three months. 



A specimen of Urticina felina was found in a sandy bay, where there 

 were no stones, with its base swollen so as to anchor it firmly in the 

 sand. A specimen of Stomphia churcUise was twice observed in the 

 mouth of a larger specimen, near which it habitually lived. There was 

 no struggle, as though the larger were trying to eat the smaller. On 

 the first occasion the observer freed the smaller one, on the second 

 occasion it seemed to be dismissed by the larger one. In the case of 

 Pcachia there is a ciliary incurrent stream which wafts in diatoms and 

 the like, and may also help in respiration. Individuals supplied with 

 Gammarus and young fish a few days old did not capture them. 



Note on Medusan Genus Stomolophus. f — Henry B. Bigelow 

 notes the occurrence of specimens of Stomolophus in San Diego Bay, 

 California, which differed strikingly in colour from their Atlantic ally, 

 S. meleagris Agassiz. But the colour differences are not accompanied 

 by any structural differences which would warrant specific separation. 

 Three other forms of Stomolophus have been described — 8. fritillaria 

 Haeckel, S. agaricus Haeckel, and 8. chuni Vanhoffen. But all must be 



* Zoologist, 1915, pp. 1-4. 



t Publications Univ. California (Zool.) xiii. (1914) pp. 239-41. 



