304 Proceedings of Royal Society of Edinburgh. [sess. 
soon found to be covered with a luxuriant growth of zoophyte .... 
a Eudendrium has been observed to cover the bottom of a boat in 
fifteen days. 
One of us has observed off the coast of the Malay Peninsula 
hydroid colonies ( Obelia , sp.) several inches in length attached to 
the cast skins of sea snakes ( Enhydrina valakadien and others). 
These therefore had grown upon the skins before the latter had 
had time to disintegrate, for such colonies were not present on any 
of the hundreds of living sea snakes examined. 
Hincks states (p. xliv) that some species of hydroids, especially 
such as grow on fronds and stems of seaweed, are annuals. The 
larger arborescent masses of the stouter kinds of Sertularia, 
Helecium , Eudendrium , etc., are, however, probably the growth of 
several seasons.* 
Some of the Siphonophora are probably annual. A species of 
P or pita f is common in calm warm weather (February to April) in 
the Indian seas, but completely disappears in the stormy season 
(about July). This animal has no power of sinking, and its com- 
plete disappearance seems to indicate that it has perished, and 
those which appear in the next warm season probably belong to 
the following generation. 
* There is a complete absence of hydranths in some forms during the winter, 
but the ccenosarc persists, and new polyps develop by budding in the following 
spring. Weismann {Die Entstehung der Sexualzellen bei den Hydromedusoe , 
p. 102, Jena, 1883) states that in Eudendrium racemosum the hydranths are 
wanting during the winter in those colonies which are situated in exposed 
stormy places, but they may persist in those which live in more protected 
situations. The hydranths of Tubularia indivisa (Allman, Gymnoblastic 
Hydroids, p. 403, Ray Soc., 1871) are in greatest perfection during spring 
and summer, and when the racemes of gonophores have attained their greatest 
size the hydranths are “ perpetually cast off and renewed.” Towards the end 
of summer the renewal of the hydranths ceases, and the upper parts of the 
perisarcal tubes are empty, and probably remain so during the winter, new 
hydranths being formed in the spring. Van Beneden ( ■' ‘ Recherches sur la 
Faune Littorale de Belgique (Polypes),” Mem. V Acad. Roy. de Belgique , 
t. 36, 1867, p. 101) records specimens of Tubularia and Campanularia which 
have lived in his aquaria for several years without any diminution of their 
powers of growth. 
f It may be of interest to refer here to w’hat we believe is the first reference 
in English to Porpita. It occurs in a letter written from Goa by Thomas 
Stee vens in 1579. In describing his voyage to India he says — “ The first 
sign of land was certain fowls which they know to be of India. The second 
was boughs of palms and sedges. The third, snakes swimming on the w r ater, 
