APRIL 29, 1897 | 
NATURE 
609 
that it had been brought about by the eating of certain 
oysters. The oyster has had so many attacks made on 
it of late, that it seems almost cruel to suggest that it 
might possibly serve as the host of this new endo- 
parasite. 
The next two writers present us in the course of their 
articles with a new classification apiece. Prof. Marcus 
Hartog deals with the Rotifers, animals which are known 
to all amateur microscopists in such beautiful and in- 
teresting forms as Melicerta ringers, with its little tube of 
pellets. It is, however, not only to the microscopist, but 
to the advanced morphologist, that the rotifers are, as 
Mr. Hartog says, “a subject of keen interest.” The re- 
semblance of some of them to the larval form known as 
a trochosphere caused Huxley, in 1851, to draw the con- 
clusion “that the Rotifera are the permanent forms of 
Echinoderm larv@, and hold the same relation to the 
Echinoderms that the Hydriform polypi hold to the 
Meduse, or that Appendicu/aria holds to the Ascidians.” 
The relation to the trochosphere has also been insisted 
on by no less writers than Lankester, Balfour, Hatschek, 
and Kleinenberg, while quite recently Haeckel has en- 
deavoured to show that such a Rotifer as Nofeus guadrt- 
corvnis presents a strong resemblance to what he, if not 
others, believes to have been the earliest type of Echino- 
derm. Mr. Hartog, however, has “been induced to 
take a view of the structure of Rotifers that brings it into 
close relationship with the lower Platyhelminthes, and 
with the more primitive larva of the Nemertines termed 
Pilidium.” 
“If we compare this organism with a Rotifer,” he 
writes, “we find that the wreath corresponds in both, 
the funnel of the disc in such forms as Flosculariid and 
Microcodon \eading to the mouth of P2/idium, while 
the gut is blind in Asplanchnidz and in some of the 
highly developed Seisonidze. The circular nerve-ring of 
Pilidiwyn is in many Rotifers only represented by its 
anterior part, the brain, though in Bdelloids a sub-ceso- 
phageal ganglion completes the ring. This leaves a diffi- 
culty with regard to the apical sense organ ; but it iseasy to 
understand that an organ of sensation should become an 
organ of fixation. In this case the foot with its glands would 
correspond to the sense organ of the Trochophore larva ; 
and it retains its primitive ciliated character in the larvee 
and males of many Rotifera, and the adult female of 
Pierodina and Callidina tetraodon. Embryology tells us 
that the anus of Rotifers cannot be homologous with that 
of Annelids, &c., for it is formed outside the area of the 
blastopore: it is an independent formation, probably 
due to the coalescence of the originally blind intestine at 
its extremity with the earlier genito-urinary cloaca. On 
this view we must change the orientation of the Rotifer, 
and place it, like a Cuttlefish, mouth downwards: for 
‘anterior and posterior’ we must substitute ova/ (or 
basal) and apical; for ‘dorsal’ and ‘ventral’ we must 
use avterior and posterior ; while ‘right’ and ‘left’ are 
unchanged.” : 
We do not altogether agree with Mr. Hartog’s views 
regarding the apical sense-organ. Nevertheless, it does 
not necessarily constitute a serious difficulty, since it is 
well known that sense-organs can be developed afresh in 
almost any part of the body where they may be required. 
The whole suggestion, moreover, is extremely interesting, 
and so far as the needs of sucha Natural History are con- 
cerned, we can have no quarrel with Mr. Hartog, seeing 
that, “‘as these views are now published for the first time,” 
he has “thought it wiser to keep to the accepted relations 
in the general description, a course which has the ad- 
vantage of avoiding difficulties in the study of the 
literature of the Class.” 
Mr. Benham, in dealing with the Polychzta, has not 
been so wise, for he adopts a classification that has 
previously been put forward, and that in a slightly different 
form, only at the meeting of the British Association in 
NO. 1435, VOL. 55] 
1894, and has not yet met with any acceptance. This: 
classification, however, he not only reintroduces, but 
permits to govern the whole. arrangement of his section. 
Apart from our strong presentiment that few workers on 
the Polychzeta will accept this classification without con- 
siderable question, we cannot think that it is altogether 
fair to the readers to introduce so great a novelty in what 
after all professes to be a popular work. Mr. ‘Benham, 
however, as we have already hinted, can hardly claim to. 
have made his contribution particularly popular, except, 
indeed, where he quotes, as we are glad to say he does 
pretty often, that fascinating and suggestive writer, Sir 
J. Dalyell. Passing to Mr. Benham’s chapter xii., we 
find that it purports to contain a “description of British 
Genera and Species.” It is true that a certain number of 
species found in the British area are described in more 
or less cursory fashion, but whereas some of the species 
so described are definitely stated to occur around our 
coasts, others are merely put down with such a locality 
as “Atlantic,” and it is not always stated whether or no 
they can be regarded as British. In other respects, too, 
this heading is not quite accurate, for many of the species 
mentioned are not described, while others which do occur 
are not even mentioned. We may note in passing that 
the curious parasite of crinoids known as Myzostoma, 
recently found, by the way, to occur also in two genera 
of starfish, is regarded by Mr. Benham as a degenerate 
Cheetopod. 
The Oligocheeta, which include the familiar earthworm, 
have been entrusted, most naturally, to Mr. F. E. 
Beddard. We notice that he includes in the group the 
little parasite of the crayfish, Branchiobdella, which, 
curiously, was omitted from his monograph. The family 
Discodrilidz, in which it occurs, is placed among the 
Microdrili. Here also comes the family Phreoryctide, 
which Mr. Beddard considers to be low in the series, 
arguing from the generative organs of P. smithiz. It 
should be noticed that Vejdovsky does not accept this 
position for the family, and would, in fact, refer this par- 
ticular species to some other genus. In other respects, 
however, there can be little doubt that Mr. Beddard’s 
account leaves small opportunities for criticism. There- 
is Just one small point m his account of the Hirudinea 
where, trying perhaps to be popular, he has fallen into. 
a not uncommon error. ‘‘ The former extensive use of 
the leech has led,” he says, “to the transfer of its name 
to the doctor who employs it, the authors of the sixteenth, 
century constantly terming a physician a leech.” There 
seems little doubt but that it was the leech which de- 
rived its name from the physician. As Mr. Beddard’s 
linguistic attainments might have shown him, the word 
leech is obviously derived from the Anglo-Saxon /ece, a 
physician, a word which we still find in Scandinavian 
languages, as in the Danish /ege. The use of /eech as 
applied to Azxuwdo medicinalis, on the other hand, is 
strictly confined to the English language. 
Following on the leeches comes Mr. Shipley with a 
remarkably up-to-date account of the Gephyrea, a group- 
of some zoological importance as having so often and 
so long been placed with the Echinoderms, in conse- 
quence of their strong external resemblance to some 
Holothurians. Mr. Shipley, following most recent 
authorities, would derive them from the Chzetopoda, 
their nearest ally in that group being Stermaspis, and 
would place the Echiuroidea nearest to that phylum,. 
while the Sipunculoidea are regarded as allied to them, 
but as having departed further from the annelid stock. 
It is perhaps a pity that the remarkable genus: 
Phoronis should have been described in the present 
volume. It is true that earlier writers supposed it an 
offshoot of the Gephyrea, and that Caldwell and 
Lankester have associated it with those animals along 
with the Brachiopoda and Polyzoa, more especially with 
the last. Mr. Shipley feels tempted to accept the recent 
