M. T. Thorell on the Arrangement of the Copepoda. 447 
are attacked by A. foliaceus, one by A. catostomi. Cyprinodonts 
have afforded A. funduli; the Characinide A. Natterert, A. sal- 
mini and G. longicauda. Salmonoids are affected by A. coreyont 
and A. foliaceus, which has also been taken on an Ksocoid; the 
Clupeide finally have contributed a species, 4. alose. Among 
the Pharyngognathi the family Chromide has a parasite in A. 
chromidis ; and among the Acanthopteri it is the families Scom- 
bride (for A. purpureus and foliaceus), Sparide (for A. pur- 
pureus), and Percide (for A. foliaceus) on which representatives 
of the Arguloid family have been hitherto observed. 
I avail myself of this occasion to refute some objections which 
have lately been put forward by Claus* against the attempted 
arrangement of the order Copepoda communicated by me in my 
memoir above cited—“ Contribution to our knowledge of the 
Crustacea which live on the species of the genus Ascidia, L.”’+ 
This arrangement (in three parallel series, Gnathostoma, Peeci- 
lostoma, and Siphonostoma) is based upon the structure of the 
organs of the mouth, which, he says “in the first division are 
adapted for chewing, in the other two for piercing and sucking. 
The arrangement of the free and parasitic in parallel series 
renders the formation of the subordinate groups more difficult, 
the three forms of mouth presenting numerous cases of transi- 
tion. It separates nearly allied forms, and, if strictly adhered 
to, produces an unnatural and one-sided system. Further, the 
character imputed to the Peecilostoma—‘ Os mandibulis et si- 
phone carens, maxillarum paribus 3—-1(-O) instructum ’—rests 
on an error, since the mandibles are very well developed.” 
To begin with the last remark, which seems to contain a charge 
of especial weight, since it would appear that Claus represents 
me as overlooking in the Pecilostoma the presence of the very 
organs (the mandibles) on the presence or absence of which the 
differences between the Gnathostoma and Peecilostoma depend. 
That such, however, is not his meaning, is apparent from an 
expression on p. 28, where we read, “ Here [in the Coryceide] 
the maxille are reduced to very simple plates furnished with 
several bristles, and have been regarded by Thorell as appendages 
of the mandibles.” In effect the differences between Claus’s and 
my notions of the oral organs of the Peecilostoma reduce themselves 
* Die frei lebenden Copepoden, p. 9. 
+ Prof. Kroyer (Bidrag til Kundskab om Snyltekrebsene, p. 82) also, 
but more summarily, attacks this attempt. -As, however, he brings for- 
ward no sufiicient objection, either against the principle adopted or the 
mode of its application, but rather confines himself to bitter invectives 
against those zoologists who, not troubling themselves with “mere de- 
scriptive work,” are yet bold enough to “put forward systems,” I shall 
treat his criticisms as they deserve. 
ol* 
