LOXOSOMA. 375 



its characteristic bend, remain absolutely the same. The gem- 

 mation need not be taken into account, for amongst the ordinary 

 Bryozoa two very different types prevail, while in all cases the 

 bud is formed out of the same tissues. Lastly, the form of the 

 embryos and their development must be studied much more in 

 detail before any conclusion can be based upon them. M. 

 Barrois, indeed, has attempted to reduce all the varying embryonic 

 forms of the Bryozoa to a single type, and the very attempt 

 shows at least the possibility of such a reduction. 



In the present discussion, the nervous and reproductive organs 

 are not in question, for we find them varying even in the most 

 nearly allied species. There remain, therefore, only the (dis- 

 tinctive) characters mentioned above, the adjuncts of the colonial 

 condition, and the altered position of the anus. 



Of these, the first need not be taken into account. In all 

 cases we do not hesitate to associate in the same class simple 

 and compound forms ; we do not pretend that the Actinice should 

 be separated from the Anthozoa, or the simple Ascidians from the 

 Clavelince. 



The only differential character, therefore, of any importance 

 will be the position of the anal orifice, on which Nitsche's pro- 

 posed division into Ectoprocta and Entoprocta is founded, a 

 division which the Author fully adopts. At the same time he 

 would not lay so much stress on this character as to make it a 

 ground for the complete separation of the two series. Both are 

 equally Bryozoa ; the position of the anal orifice cannot separate 

 them, especially as the change is really in the situation of the 

 tentacular crown and not of the anus. The latter, indeed, occu- 

 pies, amongst all the Bryozoa, Ectoprocta and Entoprocta alike, 

 the same position opposite to the mouth ; but whilst in the latter 

 the tentacular crown surrounds the two orifices, amongst the former 

 it only encloses the oral,^ 



1 I have already referred to the difference in the plan of development by 

 which the bud of the Entoprocta is distinguished from that of all the other 

 Tolyzoa, so far as it is known. The peculiarities in the structure and 

 history of the embryo also seem to me to be very important and full of 

 significance. M. Barrois, indeed, has shown that in all the tyjies of embryo 

 the early stages are identical, and he considers that a primitive form may 

 be demonstrated for the group of the Polyzoa from which all the known 

 larval modifications are derived. However this may be, it must be admitted 

 that the direct passage of tlie larva into the perfect animal, which seems to 

 distinguish tiie Entoprocta, and the peculiarities of the embryo, which 

 involve a distinct type of structure in the adult polypide, are points of the 

 highest interest and of great systematic value. Amongst the ordinary 

 Polyzoa, so far as the history of their development is known, the larva 

 undergoes a dissolution of its organs after attachment, and assumes the 

 form of a cyst or cell enclosing a mass of formative material, and the 

 polypide is produced within this cell by a process of gemmation. In Fied- 



