122 TEXTBOOK OF ZOOLOGY 



on logs either floating in the water or submerged. In some parts 

 of the country there is the idea that sponges require clear water, 

 but in the region referred to they (particularly Trochospongilla 

 horrida and Ephydatia crater if ormis) grow abundantly in muddy 

 ponds and in muddy streams whose turbidity equals 110 parts of 

 solid matter per million. In this region again the growth of the 

 sponge and apparently gemmule formation is a perennial process. 

 The maximum production of gemmules seems to be in the late 

 autumn and throughout the winter, even following periods of low 

 temperature in the spring. These gemmules are ordinarily de- 

 posited in a pavementlike layer on the object to which the sponge 

 is attached, sometimes covering several square inches. The species 

 are usually identified by means of microscopic differences in the 

 gemmule spicules as seen when crushed. 



Order Ceratosa. — A group of important sponges of which man uses 

 at least a dozen different ones. The representatives of this order have 

 skeletons of spongin and are found in subtropical and tropical marine 

 waters. Euspongia, the bath sponge. 



Order Myxospongida. — These sponges are entirely devoid of skele- 

 ton. Haliscara. 



THE SIMPLE SPONGE 



Scypha coronata* (Ellis and Solander) has been mistakenly called 

 "grantia," the European form, by most textbooks for years. This 

 is a commonly studied representative of the phylum. It is available 

 and is also comparatively simple in structure. It is not as simple, 

 however, as Leucosolenia. 



Habitat and Behavior 



This type lives attached to rocks in relatively shallow marine 

 water. The animal is attached by the basal or proximal end; the 

 opposite end is free or distal. A colony may be formed by budding. 

 Water is drawn in through the pores or ostia on the sides of the 

 body, then by way of the canals into the internal cavity. This water 

 is forced up through the cavity and out at the osculum or exit open- 

 ing at the top. The osculum and ostia maj^ be closed and there 



•A Case of Incorrect Identification American genus is Scypha. M. "W. de Lau- 

 benfels. Pasadena, Calif., Science Vol. 85, No. 2199, Feb. 10, 1937, p. 199. 



