Review of Recent Geological Lllcrature. ■41 
The development of siphonopores in the two genera is essentially dif- 
ferent, perhaps that of the autopores, though^ still 'passing under the 
name of coenenchymal gemmation. The latter is beyond doubt a singular 
and striking phenomenon (yet it occurs in the monticuliporids) and 
should perhaps serve as a preliminary index of more intimate relation. 
But when this indication is belied by a total aVjsence of structural agree- 
ment, in face of a time break from the Devonian to the Cretaceous 
without any intermediate forms, are we justified in regarding "coenen- 
chymal gemmation " as a criterion of more than class relationship? 
Certainly Nicholson was corrected in placing Heliopora and Heliolites 
in different families. Perhaps he would have done better by removing 
the latter from the Alcyonaria altogether. 
Dimorphism and coenenchymal gemmation are usually regarded as 
indicating Alcyonarian character. Of the tabulates which Mr. Sardeson 
ranks with the Alcyonaria, the majority, perhaps, possess only one of 
these peculiarities, and many possess neither. To explain the absence 
of dimorphism Mr. Sardeson considers that in the perforate-tabulate 
group, the mural pores stand as the homologs of the siphonopores in 
Heliolites et. al. That they could not be regarded as the homologs of 
autopores is evident since in that case we would have a colony without 
feeding or reproductive zooids. He regards the monomorphic form as 
probably the original type in these genera, but believes that this is not 
found in Favosites and its allies which he considers to have lost their 
dimorphism instead of not yet attained it. In other words Favosites is 
a Heliolites colony in which the siphonopores have gradually decreased 
in number until no trace of them is left except in the mural pores with 
which they are homologous. 
If this theory is correct we would expect to find this change indicated 
in some way in the embryologic condition of the corallum. Now it so 
happens that Favosites is one of the few genera with whose develop- 
ment we are somewhat familiar, and nothing of the sort is found to 
occur. Furthermore it is evident that we would have the autopores 
antedating and giving rise to the siphonopores (since Mr. Sardeson 
must admit that the connecting pores in the walls of Favosites are of 
the same nature as those which from time to time become the starting 
point for new cells), the reverse of what'is found in Heliopora and 
Heliolites. and the siphonopores not producing other siphonopores 
whether by intermural gemmati(ni as in Heliopora, or by fission as in 
Heliolites, nor developing autopores by coenenchymal gemmation. We 
would in fact have to regard each siphonopore as developing directly 
into an autopore (when it did not subsist as simply a mural opening) all 
distinction between autopore and siphonopore being lost, and all the 
individuality of coenenchymal gemmation existing in its name alone. 
The jjaijer closes with a theoretical discussion of the form of the 
corallum in colonies. Mr. Sardeson considers that the shape is con- 
ditioned by the direction from which the food supply is derived. If the 
food supjjly comes from above, vertically, the central individuals of the 
hemispherical mass grow fastest because better nourished, and the 
