182 CTENOPHORiE. Part IT. 



perceived, on aecomit of the great uniformity of the tul)es themselves. Even in 

 Pleuroljrachia, in -which the chyniiferons tulles seem aljsohitely identical in size, 

 and evenly radiating in eight directions, the same arrangement may be recognized, 

 upon carefid examination. 



In the second place, these four pairs of chymiferous tubes, so comljincd, are 

 unequal in their development, — the lateral pairs being short, and terminating each 

 in a small free lobe or auricle, while the anterior as well as the posterior pair, 

 meandering through the thickness of lobe-like prolongation of the spherosome, 

 anastomoze with one another, and form a curious lattice-work of chjmiferous tubes 

 upon the inner surflice of the base.^ 



The most striking peculiarity of all the amiiulacral chymiferous tubes of the 

 Mnemiida? consists, however, in the great inequality of the diameter of the tubes 

 in diflierent parts of their course. Upon the sides of the spherosome, and as far 

 as the locomotive flappers extend along with them, they are wide and highly 

 contractile ; but beyond these limits they are more like capillary vessels of an equal 

 diameter, especially in their prolongation upon the inner surfiice of the great lobes 

 of the si)lierosome, where those of the two sides of the anterior and of the posterior 

 pair anastomose with one another, as well as with branches from the lateral pairs 

 and from the oral tube. The centre of the whole chymiferous system is neither 

 so fully developed as in the Cydippidiu nor so reduced as in the Beroid;\' ; )jut the 

 main trunks and the axial fmniel are of moderate dimensions. The cceliac and 

 the interamlmlacral tuljes, of which there is but one on each side, run parallel to 

 one another, and present nearly the same development. The tentacular appa- 

 ratus is connected with the extremity of the interamlndacral tube, Ijut not enclosed 

 in a deep sac. The circnmscriljed area of the ahactinal pole is not more distinct 

 than in the Cydippidiv, nor are the ovaries and si)ermaries prominent. The 

 digestive cavity is comparatively small, as in Cydippida^ ; ]jut there is this re- 

 markalile difference Ijctween the Mnemiida> and Cydippid;v in the relations of the 

 actinostome, that while in (Jydippida> tlie mouth is prominent on the actinal 

 pole, in Mnemiida? the broad lobes formed by an actinal prolongation of the two 

 anterior and the two posterior spheromeres extend far beyond the mouth, and may 



^ "Whether this network of chymiferous tubes, observed in LeSueuriii and Euramjihiva, I infer 



tlius far only nuti<Td in Bolina, Alcinoo, Chiaja, and that the rectanguhir, anastomotic ramifications of 



Leucothoe by ]Mertens, Will, and inyself, exists in the chymiferous tul.ies n]ion the lower surface of 



all Mnemiidiv, or not, I am unable to say. I am, the lobe-like prolongation of the sidierosome is 



however, inclined to believe that it will bo fdund in likely to exist in all the representatives of this 



all. Its anastomosis with the recurrent tul)e of the sub-order. The appearance of this network of 



auricles seems a typical indication of its natural tubes is very similar to the mode of ramification 



connections; and as the recurrent tulie has been of the branchial vessels of the Naiades. 



