56 Journal of the Mitchell Society [Septemher 



long ray, the shaft (technically rhabdome), and three shorter rays 

 (the cladi, forming together the cladonie), which are given off from 

 the end of the shaft. In the sponge which I shall now describe, a 

 further evolutionary change has occurred, and rays are given off at 

 both ends of the shaft of the basic spicule, the spicule thus becoming 

 what is called an amjihitriaene (Fig. 1). 



The sponge referred to is a Philippine form, a new species, Jere- 

 opsis fruticosa mihi, dredged by the U. S. Fisheries Steamer Albatross 

 in 80 fathoms in the region of the Sulu Archipelago, and which will 

 be described in detail in a forthcoming report on Philippine sponges. 

 It is a stony sponge of branching-cylindrical, or shrubby, habitus, 

 55 mm. high, and with the free spicules of the genus (dichotriaenes, 

 oxeas, and streptasters including amphiasters and spirasters). In 

 the two other recorded species of the genus, Jereopsis schmidtii (Sol- 

 las) from the tropical Atlantic and Jereopsis {Neosiphonia) superstes 

 (Sollas) from the tropical Pacific (cf. Sollas 1888, Lendenfeld 1903), 

 the desma is, perhaps, the usual type of tetracrepid desma, built up 

 on a calthrops. Schmidt's figure (1879, Taf. II, Fig. 10) suggests 

 however that this is not the case. I hope at some time to have the 

 opportunity of making a critical examination of the desma, from this 

 point of view, in the type specimens of these two species. 



The facts concerning the development and structure of the desma 

 in this sponge {Jereopsis fruticosa) are as follows: 



Small, perfectly free amphitriaenes (Fig. 1) occur in the super- 

 ficial (ectosomal) region of the sponge. The spicules are about one- 

 sixth mm. long, and consist of a straight shaft with three rays (cladi) 

 at each end. The streak of peculiar substance, known as the "axial 

 canal," which is found in each of the axes of a tetraxial spicule, here 

 extends, as the figure shows, along the axis of the shaft and to the tip 

 of each ray. 



Early stages in the transformation of such spicules into desmas 

 may be found near the surface of the sponge. One is shown in figure 

 2. Such young desmas are free or only slightly connected with the 

 body of the skeleton. In them the shaft continues to be of about the 

 same length as in the basic spicule (Fig. 1), although it is thicker, 

 but the rays have greatly increased in length. They measure now 

 from one-half to the full length of the shaft or indeed slightly over. 

 They are simple, viz., not branched, and when not corroded their ends 

 bear rounded tubercles for articulation with other desmas. The axial 



