274 THE INTERCHANGEABLE RELATIONS OF 



of the Mites, (a group of Spiders,) as it does those of Shrimps. 

 It is a curious fact, though, that the male (C) of one of that 

 group of Shrimps, the Lerneans, which live as parasites upon 

 the bodies of various aquatic animals, has such a strong resem- 

 blance to the Mites, whilst the female of this same species (An- 

 chorella unclnata) has an extraordinary worm-like shape and 

 proportions, and yet, in its younger stages of growth, exhibits 

 such characters as incontestably bring it in close proximity to 

 that group of Shrimps which are known as the Cyclopida (P). 

 As an instance of diversity of opinion upon this point, I would 

 state, also, that Van Beneden thinks that the Mites, instead of 

 being classed with the Spiders, should be placed with the Lerne- 

 ans (C), and that the latter, being removed from the neighbor- 

 hood of the Cyclopidce (P), should form, in connection with the 

 Tardigrades (E, I, J), a separate class among the Articulates. 



Now, in regard to the group of Tardigrades (E, I, J), I would 

 say, that, although there has been an inclination to class them 

 with the Worms, yet the strongest tendency has been to place 

 them in the neighborhood of the Mites ; and this would seem to 

 be further warranted since the discovery of this animal, (J) Lydella, 

 with its eight long, distinctly jointed legs, and hooked claws. 

 Although this other animal, (I) Tardigrada, has the elongate 

 form of the Worms, yet its resemblance to one of the similarly 

 worm-like Mites, as represented here, (F,) a Demodex, is equally 

 striking ; and moreover the internal organization partakes much 

 more strongly of the character of the latter. It would seem, 

 therefore, that, although the worm-shaped Linguatula (A) ap- 

 pears to be linked with the Lerneans (C), Tardigrades (E, I, J), 

 and Mites (F), which Van Beneden would unite in one class, 

 yet it is equally clear that the same animal may be traced, 

 through the Mites (F) to the Spiders (G), or through the Mites 

 (F) and Tardigrades (E, I, J) to the Spiders (G), or, finally, 

 through the Lerneans (C) to the Cyclopidas (P), and from the 

 latter to the Lobsters and Crabs. 



There is another worm-shaped animal, (L) Albertia, which 

 lives as a parasite in the intestines of Snails and Earth-worms. 



