81 



dividiials. Tlu^ heads are small and somewhat flattened laterally. They 

 measure on an average Oir> mm. in length and 06 mm. in breadth. The 

 spicules are arranged in eight double rows, each containing live to seven j)airs of 

 converging spicules, one of the lowest of which may be a little longer than the 

 others. In addition to these a few spicules seem to foi'm a sort of lateral acces- 

 sory Stutzbundel. Along the aboral surface of each tentacle there are two 

 rows of small, flattened spicules, regularly arranged. 



The Stutzbundel shows considerable variation, depending on whether the 

 polyp-stalk is a direct continuation of the twig or arises from the lateral surface. 

 In the former case the Stutzbundel is very well developed, consisting of three 

 to four large spicules, of which one may reach a length of 3-2 mm. and pro- 

 ject 0'9 to 1 •() mm. At times a second spicule projects a little. In the latter 

 case it may consist of a number of spicules forming a sheath, three to four of 

 them being slightly larger than the others, and two always projecting. In the 

 youngest polyps a similar sheath is formed, but while two or three spicules are 

 slightly larger than the others, none of them project. 



Cortical spicules : (a) The stem con- 

 tains large spindles, either straight or 

 curved ; short, thick spindles ; small forms 

 approaching clubs in shape, and small 

 spherical and flattened bodies. They are 

 arranged irregularly transversely on the 

 main stem and branches, but on the smaller 

 branches and twigs take up a longitudinal 

 position. The large spindles may be 4-8 

 mm. long and 0"4.5 mm. broad ; they show 

 several interesting features — they are often 

 divided into a number of prongs at one 

 end, which, if two in number, stand at an 

 angle to one another, but if more than two, 

 lie invarial)ly parallel to one another and 

 in contact ; at the other end they are abruptly contracted and then produced into 

 a slightly curved, tapering, finger-like process. At other times they send off" a 

 process near one end which curves round and lies practically parallel to the 

 main portion of the s{)icule. All the spicules are thickly covered with })ro- 

 minent blunt, multituberculate spines regularly arranged, which in the globular 

 and flattened forms may be produced to a point. 



(b) The stalk spicules are very various, and include short, thick, blunt 



spindles ; cylindrical, globular, three- and four-rayed forms ; irregular flattened 



forms ; and spindles with one end forked. All are covered by low, blunt, 



toothed warts. 

 11 



Fig. 40. D. multispinosa. 



