44 
SUPPLEMENT 
zoophyta was replaced by that of mollusca , for the second, 
while it replaced that of lithophyta , for the fourth, which was 
suppressed. 
In the eleventh edition, the class of worms is divided into 
five orders : Intestina , Mollusca , Testacea , Lithophyta , and 
Zoophyta , and the genera which at present constitute the class 
of red-blooded worms, were parcelled out, some as lumbricus 
and hirudo in the first order ; others as terebella , aphrodita 
and nereis in the second ; and finally, some as serpula and 
sabella in the fourth, in consequence of the tube in which they 
live. 
In the interval from this edition of the Systema Naturae , 
to the last, which appeared in 1766, and which was very 
closely followed by Gmelin’s, the thirteenth, some very im- 
portant researches on the animals of the Linnaean class of 
worms, and especially on the chetopoda, or setigerous anne- 
lida, were given to the world. The labours of Pallas, in 1766, 
on the aphroditae , the nereides , and the serpulae , were the 
true origin of every thing judicious, which has been subse- 
quently proposed concerning this class of animals. He 
made the very important observation, which he had already 
applied to the mollusca proper, that the presence or absence 
of a calcareous envelope did not constitute a sufficient ground 
for placing in two separate orders, animals which, in other re- 
spects, are similarly organized. Thus he approximated together 
the aphrodita) and the nereides of the order mollusca of Lin- 
nams, and the serpula) and amphitritae of that of his testacea, 
saying, that they should form a distinct order, constituting the 
passage to the Zoophytes, and to which, he adds, may be 
joined the lumbrici, the hiru dines, the ascarides, gordius, and 
the taenia) or tape-worms ; all which has been done since, has 
been founded on this observation of Pallas. 
To two Danish naturalists, Otho Frederic Muller, and Otho 
