26 Coelenterata. 



After comparison of the Actinian fauna of the Adriatic and of the Venetian 

 lagoon Rjzzi concludes that the fauna of the latter has a special facies. Cerian- 

 thidae and Zoanthidae are absent from the lagoon and the Hexactiniae are only 

 represented by Actinidae and Sagartida (while Bunodidse and Paractidae also occur 

 in the sea) and these by fewer species. There is thus a reduced fauna due to 

 the different environmental conditions in the lagoon. Aiptasia ignea is however 

 found in the lagoon and is not recorded either from the Adriatic or the whole of 

 the Mediterranean. The typical Actinia equina does not occur in the lagoon but 

 is represented by 2 var. which are constantly smaller, and Adamsia rondeletii 

 is scarce. The author records Act. cari, equina 4 var., Ammonia sulcata 4 

 var., contarinij Sagartia viduata, Heliactis bellis, Adam, rond., Aipt. ignea and 

 diaphana. - - See also below, Arthropocla p 36, Schaffer. 



Jordan has investigated the digestion in Actiniae. Food taken into the 

 ccelenteron is acted upon by ferments which cause it to break up into small 

 particles which are then ingested by the phagocytes of the mesenterial filaments. 

 Such a preliminary breaking up of the food does not take place in Anemonia 

 sulcata. Carmine or other small particles are at once ingested by the phago- 

 cytes. The extra-cellular ferment is a tiyptic one and acts only in absence of 

 free acid. Apparently the ejection mechanism of Actiniae is inhibited by the 

 presence of soluble substances derived from the food, so that only empty shells 

 are ejected. Owing to the necessity of overcoming prey of large size some of 

 the endoderm cells have undergone modification (these cells are small with 

 compact, deeply staining contents and look like the ferment cells of many in- 

 vertebrates) they are no longer phagocytic but pour out the secretion which 

 they, in common with all the other endoderm cells, produce, into the crelenterou 

 in order to subdivide the food and so render possible the primitive process 

 phagocytosis. This auxiliary action which to a certain extent was in- 

 cidentally developed, has displaced, in higher animals, the original and essential 

 feeding process (phagocytosis). 



Fleure & Walton find that the tentacles of various anemones react to many 

 contact stimuli and, while showing some amount of differential reaction, convey 

 all kinds of unsuitable material to the mouth. The tentacles are almost com- 

 pletely indifferent to the chemical stimuli they are likely to receive under 

 normal circumstances. Motor stimuli can be communicated (1) from the lips to 

 the tentacles when the former have been stimulated (especially chemically) and 

 (2) from the tentacles to the mouth causing the latter to open when the ten- 

 tacles have been stimulated (especially by contact). Scraps of filter paper were 

 placed on the same group of tentacles about once every 24 hours, usually the 

 piece was carried by the tentacles to the mouth and very often swallowed but, 

 after a longer or shorter period, rejected as inedible. After 2 to 5 days the 

 paper is no longer swallowed and in about another 2 days the tentacles will 

 no longer take hold of it. This indicates a certain amount of persistence of 

 impressions but this persistence remains the property only of these tentacles 

 and of the part of the mouth related to them, for other tentacles, on the op- 

 posite side for instance, can be tricked subsequently at least once or twice 

 before they also exhibit the inhibitory reaction. In 6 to 10 days all traces 

 of impression are lost but the authors are inclined to think that the anemones 

 "learn" more quickly from a second set of experiments than they did from 

 the first. Sensitiveness to light varies in different individuals and in the same 

 individual according to its condition but, on the whole, the anemones with 

 white tentacles are most sensitive, those with variegated red and white less so 

 and the dark red ones are least sensitive. By alternate inflation and contraction 



