ENDOSKELETON. ANIMALS. 5 



inseparably interlocked by short clubbed or mushroom- 

 shaped processes at the ends of the branches. They are 

 also held together by processes that firmly wrap around 

 and grasp neighbouring spicules. The loose spicules 

 (dichotrioenes) that support the dermal membrane ; and 

 those forming the main skeleton, are of large size (mega- 

 scleres). The minute flesh-spicules (microscleres) are of 

 two sorts, stellate or bistellate with blunt rays (chiasters 

 or amphiasters), and style-shaped (styli), that is blunt at 

 one *end and pointed at the other. A drawing illustrates 

 the forms of the spicules. 



Presented by B. W. Priest, Esq. 

 Sollas, Chall. Rep., vol. xxv. p. 339. 



A. 9. A Siliceous Sponge (EuplecteUa aspergillum. Sub-Class 

 Hexactinellida). The siliceous spicules are six- rayed 

 (hexactinellid). Those that form the main supporting 

 framework are united by bars of silex (synapticula?) 

 secreted by neighbouring cells. The magnified forms of 

 some of the spicules that always remain free are shown in 

 a drawing. Presented by Prof. C. Stewart. 



A. 10. A Horny Sponge (Dendrilla rosea) with drawings 

 illustrating the structure and mode of development of its 

 fibres, they being secreted by investing cells known as 

 sponginblasts ; the material they secrete as spongin. 



von Lendenfeld, Zeitschr. wiss. Zool., Bd. xxxviii. 1883, 

 p. 285. 



A. 11. A Horny Sponge (Euspongia officinalis), with drawing. 



A. 12. A Horny Sponge (Dysideafragilis], \i\\h drawing. Sand- 

 grains coming in contact with the growing ends of the horny 

 fibres adhere to them, and become invested by a thin layer 

 of the same material. The amount of sand varies greatly 

 with the locality ; this specimen was obtained off Hastings. 



Presented by B. W. Priest, Esq. 

 Schulze, Zeitschr. wiss. Zool., Bd. xxxii. 1879, p. 130. 



