526 
a double sheath, there being an inner chordal sheath, an outer 
cuticular, which latter is alone present in all the higher groups, 
The skeletogenous cells, by whose activity the cartilaginous verte- 
bral skeleton is formed, arise outside these sheaths ; but whereas, 
when proliferating, they in one series remain outside, they in 
the other, by the rupture of the cuticular sheath, invade the 
chordal. This distinction enables us to discriminate between a 
Chordal sertes, which embraces the Chimzroids, Elasmo- 
branchs and Dipnoi, and a Perichordal, consisting of the 
Teleosts, Ganoids and Cyclostomes. 
In consideration of the enormity of the structural gap between 
the cyclostomes and the higher Vertebrata this is an extra- 
ordinary result. For be it remembered that, in addition to 
their well-known characters; the lampreys and hags (1) in the 
total absence of paired fins; (2) in the presence of branchize, 
ordinarily seven in number, fourteen in Biledlostoma polytrema, 
numerically variable in individuals of certain species between 
six and fourteen, and doubtfully asserted in the young of one 
to be originally thirty-five ; and (3) in the carrying up of their 
oral hypopophysis by the nasal organ, whereby it perforates the 
cranium from above, as contrasted with all the higher Verte- 
brata, in which, carried in with the mouth-sac, it perforates it 
from beneath, exhibit morphological characters of an extra- 
ordinary kind. And if we are to express these characters in 
terms, we may distinguish the Cyclostomes as af/erygza/ and 
epicraniate, the higher Vertebrataas hyfocranzate.1 But this not- 
withstanding, the aforementioned subdivision of the Pisces into 
two series, which would associate the teleosts and ganoids with 
the cyclostomes, as distinct from the rest, receives support ‘from 
recent study of the head-kidney by a Japanese, who seeks to 
show that the organ so called in the Elasmobranchs is of a 
late-formed type peculiar to itself; and it is also in agreement 
with one set of conclusions previously deduced from the study 
of the reproductive organs. : 
To deal further with the fishes is impossible in this Address, 
except to remark that recent discovery in the Gambia that the 
young of the Telecstean genera Heterotis and Gymnarchus bear 
filamentous external gills, renders significant beyond expecta- 
tion the alleged presence of these among the loaches, and 
shows that adaptive organs of this type are valueless as criteria 
of affinity. ; 
In paleontology, as in recent anatomy, our records of detail 
have increased beyond precedent, often but to show how 
deficient in knowledge we are, how contradictory are our theories 
and facts. 
In dismissing the fishes, I wish to comment upon our accepted 
terms of orientation, To speak of the median fins as dorsal, 
caudal and anal, of the pelvic as ventral, and of the pectoral 
in ils varying degrees of forward translocation as abdominal or 
thoracic, though a convention of the past, is to-day inaccurate 
and absurd. I question if the time has not come at which the 
terms thoracic (pulmocardiac) and abdominal are intolerable, as 
expressing either the subdivisions of the body-cavity or any- 
thing else, outside the Mammalia, which alone possess a dia- 
phragm. Even in the birds, to grant the utmost, the sub- 
division of the ccelom, if accurately described, must be into 
pulmonary, hyper-pulmonary and cardio-abdominal chambers ; 
while with the reptiles the modes of subdivision are so complex 
that a special terminology is necessary for each of the several 
types extant. 
In the fishes, where the pericardium is alone shut off, the 
retention of the mammalian terms but hampers progress. This 
was indeed felt by Duméril, when in 1865 he attempted a re- 
visionary scheme. Since, however, one less fantastic than his 
seems desirable, I would propose that for the future the ‘‘ anal” 
fin be termed vev¢ra/, the ‘ ventral” pelvic ; and that for the 
several positions of the pelvic, that immediately in front of the 
vent, primitive and embryonic (which is the position for the 
Elasmobranchs, Sturiones, Lower Siluroids and all the higher 
Vertebrata), be termed frocta/, the so-called ‘‘ abdominal ” 
pro-proctal, the so-called ‘‘ thoracic ” jugudary (in that it denotes 
association with the area of the ‘‘collar-bone”), and the so- 
called “‘ jugular” menta/. The necessity for this becomes the 
more desirable, now that it is known that a group of Cretaceous 
fishes (the Ctenothrissidze), hitherto regarded as Berycoids, are 
1 It is an interesting circumstance, if their ‘‘ciliated sac’ 
homologised, that Amphioxus and the Tunicata present a corresponding 
dissim arity, allowance being made for the fact that in Botryllus, Good- 
siria and Polycarpa the sac overlies the ganglion. It is pertinent here to 
recall the ammoccete-like condition of the ‘‘endostyle” in Ozkopleura 
Habellum 
is rightly 
NO. 1717 VOL. 66] 
NATURE 
[SEPTEMBER 25, 1902 
in reality of clupcoid affinity, despite the fact that at this early 
geologic period they had translocated their pelvic fin into the 
jugular (‘‘ thoracic’) position. 
The sum of our knowledge acquired during the last twenty- 
eight years proves to us that, among the bony fishes, the struc- 
tural combination which would give us a premaxillo-maxillary 
gape dentigerous throughout, a proctal pelvic fin, a heart with 
conal valves, would be the lowest and most primitive. Inas- 
muchas this character of the heart, so far as at present known, 
exists only among the Clupesoces (pikes and herrings and their 
immediate allies), these must be regarded as lowly forms; 
wherefore it follows that the possession of but a single dorsal 
fin is not, as might appear, a necessary index of a highly modified 
State. 
Before I dismiss the vertebrates, a word or two upon a recent 
result of morphological inquiry which concerns them as a whole. 
I refer to the development of the skull. Up to 1878 it was 
everywhere thought and taught that the cartilaginous skull was 
acompound of paired elements, known as the trabeculz cranii 
and parachordals, and that the former contributed the cranial} 
wall. Huxley in 1874, from the study of the cranial nerves of 
fishes, had reiterated the suggestion he made in 1864, when 
dealing with the skull alone, that the trabeculz might be a pair 
of prae-oral visceral arches, serial with those which support 
the mouth and carry the gills. The next step lay with the 
Sturgeon, in which in 1878 it was found that the cranial 
wall is originally distinct. And later, when the facts 
were more fully studied in sharks, batrachians, rep- 
tiles and birds, it became evident that the trabeculze, 
though ultimately associated with the cranial wall, 
take no share in its formation, and that when first they appear 
they are disposed at right angles to the parachordals and the 
axis, serially with the visceral arches behind. Huxley was 
right ; and although this consideration by no means exhausts 
the category of independent cartilages now known to contribute 
to the formation of the skull, it proves that the cartilaginous 
cranium, like the bony one, which in the higher vertebrate 
forms replaces it, is in its essence compound. 
I now pass to the Invertebrata. Of the Oligocheta and 
Leeches I have spoken, and we may next consider the Arthro- 
pods. Of the Insecta, our knowledge has gained precision, by 
the conclusion that the primitive number of their Malpighian 
tubes is six, and by the study of development of these in the 
American cockroach Doryphora, which has rendered it probable 
they may be modified nephridia, carried in as are those of some 
oligocheetes with the proctodeal invagination. An apparent 
cervical placenta has been discovered in the orthopteran 
Hemimerus, which would seem to suggest homology with the. 
so-called ‘ trophic vesicle” of the Peripatoids, as exemplified by 
P. Novae-Britannica. In this same orthopteran there have 
been recognised, in secondary proximity to the ‘‘ lingua,” re- 
duced maxillulze, which, fully developed and interposed between 
the mandible and first maxilla, in Japyx, Machilis, Forficula 
and the Ephemera larva, give us a fifth constituent for the 
insectan head. And when it is found that all the abdominal 
segments of the common cockroach, when young, are said to 
bear appendages, of which the cerci are the hindermost, we 
have a series of facts which revolutionise our ideas. Little Jess 
striking is the discovery that in the caterpillar of the bombycine 
genera Lagoa and Chrysopyga seven pairs of pro-legs occur. 
The fuller study of the apertures of the tracheate body has re- 
sulted in the discovery that the Chilopoda are more nearly 
related to the Hexapoda than to the Diplopods ; wherefore it 
is proposed to reclassify the Tracheata, in accordance with the 
position of the genital orifice, into Pro- and Opistho-gonata. 
In a word, the ** Myriapoda,” if a natural group, are diphyletic. 
Our knowledge of the Peripatoids (4rthropoda malacopoda) 
has increased in all that concerns distribution and structure. 
They are now known, for example, from Africa, the West 
Indies, Australia and New Zealand, and for examples from the 
two latter localities and Tasmania the generic name Ooperipatus 
has but lately been proposed, to include three species, character- 
ised by the possession of an ovipositor, of which two have been 
observed to lay eggs. 
Work upon the Crustacea in our own land, notorious for the 
tendencies of some of its devotees in their stickling for priority, 
has within the last twelve years advanced beyond all expecta- 
tion. Much of our literature has been systematised, and an 
enormous increase in our knowledge of new forms has to be 
admitted, thanks to memoirs such as those of the ‘‘ Investigator,” 
