Sponges. 
197 
tures and even of the channels, in the other by increased size of the apertures and 
channels. The freshwater sponges, however, and the two species of Tetilla are in each 
instance closely related forms, not, as in that of the sponges at Port Vv'eld, belonging 
to different families. In both instances, moreover, the chief danger is that of water 
containing inorganic particles liable to cause obstruction in the canals of the sponge ; 
the danger of desiccation hardly entered into the question. Moreover, we know of 
cases, such as that of Spongilla alba in the Gangetic delta, in which the adaptations of 
sponges living in muddy water are physiological rather than structural. 
Family HAPLOSCLERIDAK. 
Reniera implexa, Schmidt. 
1868. Reniera implexa, Schmidt, Spong. Algier, p. 27. 
1887. Reniera implexa, RidiXey Dendy, " Challenger " Rep . X.'K, Monaxonida, 1^, \A. \, 
fig- 4- 
1892. Siphonochalina mollis, Topsent, Res. Camp. Sci. Monaco 11, p. 66. 
1903. Reniera implexa, id., ibid, xxv, p. 244. 
1905. Reniera implexa, Deudy, Sponges, in Herdman's Rep. Ceylon Pearl Fish, in, p. 142. 
1914. Reniera implexa, Annandale, Rec. Ind. Miis. X, p. 151. 
This species is variable in the size of its spicules, the structure of its skeleton and 
the direction of its main growth. A constant specific character is, however, that 
the sponge consists of a mass of more or less cylindrical tubes with large oscula at their 
free extremities and of hollow structure. In typical specimens from the Adriatic and 
in those from the Azores (of which one is figured by Ridley and Dendy) the tubes are 
vertical, but in all those I have examined from India and Malayan waters they are 
recumbent or semi-recumbent. 
In the collection of the Zoological Survey of India there are examples from three 
localities, from a rock-pool at Bandra near Bombay, from Madras harbour and from 
Port Weld. Those from the two Indian localities agree with the specimens from 
Ceylon described by Dendy as "consisting of a few irregularly branched tubes." In 
one from Madras harbour, fixed to a mussel-shell, there are only two tubes, which are 
only 2*5 mm. in diameter. Others from Bombay are rather better developed, but the 
tubes are not more than 5 mm. in diameter. Specimens from Port Weld originally 
formed a rather dense network covering a considerable area and confused with the 
growth of the new variety of Amorphinopsis excavans described below. Their tubes 
are sometimes as much as 7 mm. in diameter but are less regular in shape and uniform 
in diameter than in some specimens. 
The following are average measurements of spicules from the three lots of 
specimens : — 
Madras. Bombay. Perak. 
I^ength of spicule . . 0-096 mm. 0116 mm. 0-152 nmi. 
Greatest breadth of 
spicule . . 0*0038 mm. 0-0054 i^i"''^- 0-0063 mm. 
In spite of these considerable differences in size and proportions, the spicules agree 
in general form, being very sharply and gradually pointed and as a rule slightly bent. 
