314 E. A. MINCHIN. 
the stalk of C. lacunosa, and probably to many other cases 
also. In all the species of Clathrinide in which.I have 
been able to follow the development, the first spicules formed 
after the metamorphosis are triradiates, and monaxons, if 
present, appear much later. On this account I am inclined 
to doubt if primary monaxons occur at all in Clathrinide. 
In the few cases in which I have found developing monaxons 
in species of Clathrina, there were several formative cells 
attached to them, at least four, and not two only, as in 
Leucosolenia. I had greatly hoped to have been able to 
study the development of monaxon spiculesin Clathrinide, 
the only thing required to complete our knowledge of the ~ 
formation of spicules in Homoccela. I must, however, leave 
this task to others, and can only say at present that there is 
some evidence for believing the monaxons of Clathrinidz 
to be of secondary nature. I may add that there is no reason 
why secondary monaxons should not occur in Leuco- 
soleniide, but there is at present no evidence that they do. 
Maas’s statements raise a presumption in favour of the occur- 
rence of secondary monaxons in Sycons, but his single 
observation does not convince me on this point.! 
According to Maas (1900 [1], p. 44; [2] p. 225) the small 
monaxons of Sycandra setosa grow at first slowly within 
a cell, until they project from the cell and from the tissue, 
and then a sudden, rapid growth of the spicule takes place, 
hke the shooting out of a crystal (“ Krystallartiges Anschi- 
essen”’). If Ihave understood the author’s meaning rightly, 
he considers the portion of the spicule imbedded in the 
tissue as the older part, and the portion projecting into the 
water as a more recent formation. My observations lead, 
however, to an exactly opposite conclusion. The develop- 
ment of monaxon spicules possessing a lance-head shows 
clearly that the distal extremity of the spicule is the part first 
formed, and the proximal portion is the last to be secreted by 
the scleroblast. 
1 T consider it possible that the bayonet-like monaxons described by me 
(1905 [2]) in Leucosolenia variabilis (l. ¢., text-figs. 95, 16 y, 17 a, 4) 
and L. botryoides (l.c., text-figs. 98, 25 2, 7) might be reduced triradiates. 
