THE SPONGES. 17 



although the principalia Iiere exhibit the usual modification. The free 

 portion of the root tuft is 3 mm. in diameter, and includes about 12 

 spicules, which are in the neighborhood of 400 {x thick, none exceeding 

 450 fx in thickness. 



In the smooth principal oxyhexacts the rays are 250 to 850 fx long, with 

 a basal thickness of 12 to 40 fx. In the peripheral region of the paren- 

 chyma these spicules are abundant, and for the most part regularly dis- 

 posed, so as to produce roughly cubical meshes. In the deeper part of the 

 parenchyma the hexacts are rare, and are arranged without regularity. 



The smooth oxydiacts measure 750 to 1700 fx in length, with a thick- 

 ness of 8 to 20 /a near the median enlargement. They are comparatively 

 scarce in the dermal membrane and peripheral parenchyma, but \ery 

 abundant in the deeper parenchyma, where they run in all directions, 

 often arranged more or less distinctly in bundles. 



In the smooth, hypodermal oxypentacts there is no trace of the distal 

 ray. The tangential rays vary from a length of 200 /x, with a basal thick- 

 ness of 16 [X, to a length of 1000 fx, with a basal thickness of 80 jx. The 

 proximal ray is commonly half again, or twice as long as the tangential 

 rays. The spicules are very abundant, and almost alone are concerned in 

 forming the hypodermal meshwork, hypodermal diacts being rare. 



The smooth micro-oxyhexacts are very abundant throughout the paren- 

 chyma. The rays are 24 to 30 fx long, slender and straight nearly to 

 the end, where they are rather suddenly and distinctly curved. 



The dermal pinules are very long and slender. The tangential rays 

 are nearly cylindrical and then rather suddenly pointed, beset with scat- 

 tered sharp microtubercles. On the distal ray the teeth are sharp and 

 short, not exceeding 10 jx in length (measured along upper border of 

 tooth), becoming gradually reduced in size toward the upper ai'd lower 

 ends of the ray. The upper end of the distal ray in the spicules scattered 

 over the general surface is broken off, but the ray becomes very slender 

 above, and the shape indicates that it terminates in a long point. In the 

 common sizes of this spicule the tangential ray measures 60 to 00 fx long 

 by 12 fx thick ; the distal ray, 750 to 900 /x long, thickness of the lower 

 smooth part of ray, IQ fx. At the extreme lower end of the specimen the 

 pinules have distal rays only about ^ as long as elsewhere. In Schulze's 

 type specimen the dermal pinules had a distal ray 300 to 400 jx long. As 

 regards this point, therefore, my specimen differs from the type, but the 



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