HISTORY OP THE SUBJECT. 39 



first sub-class of his Helminths (Sterelmintha), the second order being the Trematoda. He 

 states that "the Turbellaria come nearer to the Trematoda than they do to the Suctorial 

 Annelids, which latter, be it remembered, are furnished with a complete intestinal tube and anus; 

 and, moreover, their characters, by the intervention of the Planarians, are too closely linked on to 

 the Trematoda to permit their being elevated by themselves into a separate class." He divides 

 the Turbellaria into two families, Planariadce and Nemertida. Further, " in common with the 

 Trematoda, the Turbellarians have their bodies composed of soft parenchymatous tissue, and in 

 this loose substance the various specialized organs are lodged, without the intervention of any 

 perivisceral cavity. Some of the animals have a flattened form, others are cylindrical, while a 

 third kind are remarkably attenuated, and more or less barred by transverse rugae, which form, as 

 it were, a series of spurious joints or articulations. The mouth and digestive apparatus are well 

 developed, but there is no certain evidence as to the existence of an anus in any of the species/' 

 It is not the case that the Turbellarians (any more than the Flukes) have their bodies composed 

 of " soft parenchymatous tissue/' for their cutaneous and muscular systems are highly developed and 

 differentiated ; and, while the Planarians are no doubt allied in external form, and in the branched 

 condition of their digestive system, to the Trematoda, yet they are still more closely connected 

 with the Nemerteans, which diverge so much from any parasitic worm recorded by this or any other 

 author. With as much reason, I fear, we might place Sagitta amongst fishes, and Amphioxus 

 amongst worms, as assert that " the Nemertidee very closely resemble the common tapeworms, or 

 Cestodes, properly so-called — not only by their band-like forms, but more particularly by their 

 tendency to display transverse rugae, which, as before remarked, acquire a certain degree of 

 regularity." His observations on the anatomy of the Nemerteans are behind date ; and in the recent 

 'Supplement' 1 he seems to have avoided the subject altogether. From what I have seen of the 

 structure of the Flukes and Tapeworms, there would appear to be a considerable margin left for 

 the minute anatomical investigators of the future. 2 



The Nemerteans are placed by Dr. Johnston, in the • Catalogue of the British Museum,' 

 under Ehrenbergs order Turbellaria, forming the second sub-order Teretularia of De Blain- 

 ville. 3 Considerable errors still remain in the author's views as to the structure of the group ; 

 thus the mouth is stated to be terminal, and to give passage to the proboscis ; while the anus is 

 said to open well forward on the ventral surface in some, and in others at the posterior extremity. 

 The mouth in the Anopla is called a genital orifice. Little is added to the information previously 

 published by the author or others up to the time of his lamented death ; and thus the work 

 is thrown far behind date. His two genera, Ceplialothrix and Astemma, are synonymous, 

 while the others pertaining to the Enopla and Anopla are so mixed up that the value of the work 

 is greatly impaired. Several species are described more than once under different names. 

 Still further confusion is propagated in the Appendix by the observations, under the general 

 characters of the Teretularia, that there is no anus ; that there are two hearts ; and that the 

 female aperture (often mistaken for a mouth) is situated, " sometimes below the head, sometimes 

 large and sucker- like, sometimes posterior and nearly terminal, when it has been mistaken for an 



1 London, 1869. 



2 The recent paper on the latter group by Professors Sommer and Landois bears ont the above 

 remark, which was penned more than three years ago. See ( Zeitsch. f. wiss. Zool/ for March, 1872. 



3 ' A Catalogue of the British Non-Parasitical Worms in the Collection of the British Museum/ 

 London, 1865. 



