the Morphology of the Blastoidea. 423 
their affinity lies; and as no living Blastoids are known, it is 
difficult to understand the similarity of the visceral cavities of 
the two groups, especially when one remembers that the hydro- 
spires of the Blastoids are wanting in the Echinoids. 
The jointed appendages of the ambulacra of the Blastoids, 
the so-called pinnules, are briefly described by Dr. Hambach, 
who rightly states that they are not placed over the marginal 
pores of the ambulacra, as supposed by many authors; but he 
goes on to make the following extraordinary statement :— 
“‘ These poral openings, as it appears, must have remained 
free ; because we frequently find the remains of collapsed 
tentacles preserved in them, the so-called supplementary poral 
pieces.” Further on also he speaks of the poral fissure at the 
side of the ambulacra “ from whence the tentacles originate, 
leaving the interior of the calyx through the poral openings, 
and forming in their collapsed state the supplementary poral 
plates of Dr. Romer. This can easily be observed in good 
and suitable specimens by grinding off the lateral margin of 
an ambulacral field, where we will find that the interior cir- 
cumference of a poral opening is lined with a membranaceous 
integument.” 
He explains rightly enough that the cavities of the hydro- 
spires communicate above with a tube extending along the 
length of the ambulacrum, and that this ‘ ovarian tube” hag 
its outlet through one of the spiracles at the summit; but he 
totally ignores the proofs given by Rofe, Billings, Wachs- 
muth, and others that the marginal pores along the ambulacra 
lead down into this ovarian tube. Surely this obvious fact 
cannot have escaped his notice during “ his numerous exami- 
nations of cross sections” of the ambulacra, unless, indeed, he 
means to imply that the “ovarian tube” also lodged a vessel 
from which the tentacles were filled. 
I had quite hoped that, since the researches of Rofe and 
Billings, the old doctrine of the ambulacra of the Blastoidea 
being fringed with tentacles like those of the Crinoids had 
been finally got rid of; and I am somewhat surprised at its 
revival by Dr. Hambach, who must have a wonderful power 
of imagination ; for he actually believes that “soft and mem- 
branaceous organs, such as occupy the pores of the ambulacral 
field in Echinoderms,” can have been preserved (in a col- 
lapsed state, it is true) through all the ages between the Car- 
boniferous period and the present time. He does not, however, 
vouchsafe to tell us when or how they underwent such changes 
as rendered them now liable to be described and figured as 
calcareous plates of definite shapes in different species of 
Blastoids. It is certainly a very singular phenomenon that 
