LUBBOCK ON BPH^RULAIlIA BOMBI. 55 



helminthologists, class it with tlie true Nematodes. The absence of an 

 organ is, however, not generally so important a character as its struc- 

 ture : thus, for instance, we see in insects, that the absence of wings is 

 less significant than are the differences in their structure, so that we have 

 wingless representatives of all the large orders. The characters which 

 induce us to separate Sphseralaria, Gordius, and Mermis, from the Ne- 

 matodes being principally negative, are not to my mind quite satisfac- 

 tory. Schneider differs also so much from Meissner as to the ana- 

 tomy of Gordius and Mermis, that it will be necessary to say a few 

 words on this subject, before considering the affinities of Sphaerularia. 

 The so-called supra- oesophageal ganglion of Mermis he denies to be a 

 portion of the nervous system at all, and considers it rather to be an 

 oesophageal bulb, homologous with what is found in many Nematodes. 

 If this be granted, the principal argument in favour of the nervous na- 

 ture of the so-called peripheral nerve-system falls to the ground, and 

 with it one of the principal differences between Sphaerularia and Mer- 

 mis. "While, however, we know nothing about the nervous system of 

 Sphaerularia, and are in such a state of uncertainty as to that of Gor- 

 dius and Mermis, it is evident that we cannot avail ourselves of it for 

 the purposes of classification. Meissner's extraordinary account of the 

 digestive organs in Mermis is well known. According to him, the oeso- 

 phagus is open along one side, thus constituting a trough rather than 

 a tube, which sends out from time to time lateral branches, each of which 

 terminates in a spherical cavity, which he calls a stomach-cell. Ac- 

 cording to Schneider, however, the oesophagus is a closed tube, and 

 the " stomach-cell" is only a round, firm body, containing a nucleated 

 structure, but without any central cavity, or any communication with 

 the fat-body. This " fat-body" is probably homologous with the intes- 

 tine of ordinary Nematodes, but no cavity has been developed in it; and 

 while Meissner describes thirty connecting tubes between it and the 

 oesophagus, Schneider denies that any such junction takes place; the 

 two organs lie side by side, but have no communication with one ano- 

 ther. 



Schneider exemplifies this by the case of Ascaris rigida, it., in which 

 the oesophagus opens, not at the anterior end, but at the side of the in- 

 testine. If, he says, this condition were exaggerated, and the lateral 

 connexion removed, we should have exactly the case of Mermis. In 

 Mermis albicans the fat-body consists of two rows of large cells, as in 

 Sphaerularia ; but in Gordius the cells are much smaller and more nume- 

 rous, still, however, solidly filling the tube; while in Mermis nigrescens 

 the cells are smaller, and only clothe the outer tube, and leave a large 

 central cavity; thus completing the series, and giving us a most interest- 

 ing gradation, connecting the corpus adiposum of Sphaerularia with the 

 ordinary intestine of any common Nematode. This corpus adiposum, 

 therefore, is homologous, not with the whole intestinal canal of Nema- 

 todes, but only with the intestine ; and we find, in fact, that in 

 Gordius the oesophagus is very short, and opens at once into the anterior 

 end of the corpus adiposum ; so that, to pass from this genus to Sphaeru- 



