618 : Recent Literature. | September, 
row, so that we are led to distinguish in certain types, the pres- 
ence a little after the gastrula stage of a stage with an aboral mass 
and extended or widened face separated one from the other by 
the furrow (Fig. 3, sd). Hence he distinguishes two fundamental 
orms; that which presents in the em- 
bryos the division into an aboral and 
Escharine or sessile form. Barrois con- 
siders that the latter is the original 
‘to the closure of the blastoderm in Clepsine and in Euaxes. The 
Ectoprocts pass during the period of their development through an 
Entoproctous condition in which the part which represents the 
intratentacular space or basilar plate, which separates the digestive 
cavity from the cavity of the sheath, contains the two openings 
of the digestive tube, and is completely encircled by the tentacles. 
Barrois thinks, contrary to Allman, that it is much more 
‘ natural to consider the Ectoprocta as organisms throughout com- 
parable to Entoprocta, but in which the anus curves within the 
tentacular crown, as he had shown to be the case at the time 
when the tentacles bud out; and it is very improbable that the 
transitory state in which the crown is interrupted on the anal side 
is the point of departure of the formation of the lophopore; we 
shall thus have a general phylogeny of the class of Polyzoa, 
based on the evolution of the tentacular crown, and disposed as 
follows: Entoproctes—Lophopodes—Gymnolemes. 
He considers that all the different larval forms of Polyzoa may be 
reduced to a single type composed of a gastrula with two opposite 
faces or ends separated by the crown, one (aboral) bearing in its 
centre the buccal opening, and capable of being covered so as to 
form the vestibule; all the larva possess a median muscular or 
fatty layer (#7), which is generally composed of a portion formed by 
the oral face (labial mesoderm) and of a portion dependent from 
the aboral face ; this last is more constant, more voluminous, and 
constitutes the essential portion of the mesoderm; it is derived 
in most cases from a simple delamination of the exoderm, but 
in the Entoproctes, the intestine appears also to take part in its 
formation ; it is even possible in Pedicellina that it is derived from 
a fold at the end of the intestine, and that we may find in the 
Polyzoa some traces of an enteroccele. 
_ From this primitive type, already very complex, the larve of 
the Entoproctes are derived by a differentiation of the mesodermic 
` 1 In all the figures o indicates the mouth; sé and si, the furrow; c, the crown of 
= Cilia, má, aboral mesoderm ; c, ciliated crown ; est, stomach, 
