187 



these the secondary twigs diverge in all directions, but all have their growing 

 tips pointing upward. The average diameter of these is about 3"5 mm. at 

 their origin, but many terminate in club-shaped processes which increase this 

 measurement to about 6 mm. Owing to excessive growth in the cfcnenchyma, 

 the angle between a twig and its support becomes almost obliterated ; so that 

 a branch 2)resents a somewhat palmate appearance, with short blunt digitiform 

 processes —the growing tips of the twigs (Plate VI. fig. 2). 



The next largest specimen is much damaged and may be the basal portion 

 of a very large colony. The main stem, which is incomplete, is 7 cm. long and 

 has a diameter of 9 mm. at the base, diminishing to 4 nun. at the broken tip. 

 The branches which arise from it do not seem proportionate to the main stem, 

 but there is evidence of the broken remains of larger bi-anches now quite over- 

 grown by the general coenenchyma. The sinuous and cylindrical character of 

 the branches is a marked feature. 



The other four colonies whose measurements are given agree most closely 

 with the third specimen. 



Thus we see that the general tendency in this species is towards an upward 

 bushy growth, but in the largest and most complete specimen (Plate VI. fig. 1) 

 the twigs were directed mainly towards one aspect. 



Another remarkable feature of the most perfect specimen is that there is no 

 hintofattaclmient. The 

 basal portion is very 

 thick and has evi- 

 dently been broken 

 from its support, but 

 it is now completely 

 overgrown by the 

 coenenchyma. This 

 secondary growth is 

 to be seen in the case 

 of another branch in 

 this specimen, and is 

 not of infrequent oc- 

 currence in several of 

 the others. May not 

 this circumstance, to 

 a great extent, explain the unilateral direction of the growing points of the 

 branches in this specimen, as contrasted with the typical form in the others ? 

 Having become detached from its support, and with a tendency to lie hori- 

 zontally, the colony would produce branches towards the upwardly directed 

 surface. It seems to us that this consideration is worthy of attention in 



Pig. 77. Spicules from ccsnenchyma of Isis hippuris. 



