Afisceliutiroii.f, 7iJ 



Up. 2. Transverse sortion of a youii^'- fmni of lihtxlojihiiUuin. Lower 

 CarboiiifiToiis, Hrocklcy, iicnr lit'siimhai^ow. 



Fig. 3. Rhodtiphylluni, sp., lon^jritiitliiml section, showing the densely vesi- 

 cular clinracter of the central ar.a ; 8 a, transverse section of the 

 same. Lower Carboniferous, Lang^side, near Beith, Ayrshire. 



Tlatk hi. 



Figs. 1-7. Transverse and longitudinal sections of a group of forms trans- 

 itional between lihoilophtjUum and AspidophyUuni. Lower 

 Carboniferous, Rrockley, near Lesnialiapow ; Thirdpart and 

 Langside (Quarries, near Heith, Ayrshire. 



MISCELLANEOUS. 



On tlie Einhryuloijij of tlie Nemertina. By M. J. Baerois. 



I HAVE already disputed the line of demarcation hitherto established 

 between the two kinds of development of the Xemertina (development 

 by the difforenliation oi aMonda, and development by the coiilescence 

 of four discoidal plates) ; I have shown that the four suckers of 

 Miiller were not, as has always been supposed, peculiar to the Pili- 

 dium, but that they occurred in types hitherto regarded as originating 

 from the direct dittereutiation of the Morula. 



Soon afterwards I succeeded in discovering the true signification 

 of the four suckers; I found that tlie two anterior smokers institute 

 tfu wjthalic muscular inas.'ies, and tlie two posterior t/ie delicate laminen 

 which form tlie wall of tlve hoibj. 



This statement is exceedingly important ; for we find in the deve- 

 lopment of all the Xemertians, even of those in which the develop- 

 ment is most simple, a stage in which there is a clear division into 

 two cavities, round each of which the various parts just mentioned 

 are formed, between the two the lateral organs and the oesophagus ; 

 round the first the cephalic masses, and round the second the laminae 

 of the wall of the body. In the Knopla this division into two cavities is, 

 from the first.vcry distinct. It is in the Anopla with a simpler deve- 

 lopment, such as Cephalothruv, that the matter is most difficult of recog- 

 nition. In consequence of a peculiarity of structure belonging to this 

 group, the two cavities appear in it, from the first, united into a single 

 one ; nevertheless it is not difficult, especially after the differentiation 

 of the two great diWsions of the musculature, to recognize without 

 hesitation their distinct existence. 



The constant and universal occurrence of this important stage, 

 whatever the group may be, enables us easily, starting from this 

 common point, to trace the divergences which give rise to the two 

 great divisions of the Anopla and the Enopla. 



Two phenomena are necessary to form one of the Anopla : — 1. The 

 lateral organs detach themselves from the oesophagus, and the pro- 



