50 PROF. G. B. HOWES AND MR. H. H. SWINNERTON ON THE 
anteriorly with the basal ethmoid, united by their postero-internal extremities with 
the parachordal; and, what is more, they are serially disposed at all stages with the 
visceral skeletal arches. 
Recent investigation by the reconstruction method has led to the conclusion that 
the developmental processes occurring in the skull of Man himself are not easily 
reconcilable with those generally believed to be passed through by even that of certain 
other mammals !. 
As is well known, Salensky in 1878 described? in the embryo Sturgeon a distinct 
cartilaginous centre for the lateral cranial wall; and Stohr, in 1880, discovering that 
the parachordal of Triton? appears in two pieces, in 1882 showed* the basal portion of 
the chondrocranium of Rana to be complex, if not actually composed of three pairs 
of distinct elements—trabecule, ‘“‘ mesotic cartilages,” and ‘ occipital plates” (para- 
chordals). Miss Platt has later described in Necturus® the dorsal part of the “ crista 
trabecule” as paired, and instituted, on consultation with Sewertzoff, a comparison 
with the alisphenoidal cartilage originally described by him in Acanthias in 97% 
While Peter, in the same year as Miss Platt, recorded the formation in Ichthyophis’ of 
so-called “dorsal trabecule.” Most important of all, however, is the full monograph 
of Sewertzoff, which has appeared during the progress of our work, in which *, bringing 
the whole subject to a focus, he shows that in the Klasmobranch Acanthias the trabecule 
take an insignificant share in the formation of the lateral cranial wall, and that this is 
mainly formed on either side from the above-mentioned distinct cartilages (termed by 
him the alisphenoidal), the pair of which, uniting with the trabecule, contribute what 
he has termed the prochordal portion of the resulting chondrocranium. In his 
memoir he meets the challenge that if this cartilage be of the importance he claims, it 
should be more generally forthcoming, by showing reason for its being present in 
Pristiurus, that W. K. Parker had seen it in the Salmon®, and that other 
observers, and more particularly Miss Platt and Peter referred to above, had probably 
done so in other chordate forms. In view of this and of the similarity in posterior 
extension of the trabecule along the parachordal in Acanthias and Sphenodon, and of 
the relationships of the latter to our otosphenoidal plate (PI. III. fig. 1), we consider 
that this may perhaps represent Sewertzoff’s alisphenoidal cartilage 1°. 
‘ Levi, G.: Archiv mikr. Anat. Bd. ly. 1900, p. 407. 
* Salensky, W.: Zool. Anz. Bd. i. 1878, p. 289. 
Stohr, Ph.: Zeitschr. wiss. Zool. Bd. xxxiii. 1880, p. 477. 
Stohr, Ph.: Ibid. Bd, xxxvi. 1882, p. 91. 
’ Platt, Miss Julia: Morph. Jahrb. Bd. xxv. 1897, p. 377. 
* Sewertzoff, A.: Anat. Anz. Bd. xiii. 1897, p. 413. 
7 Peter, K.: Morph. Jahrb. Bd. xxv. 1898, p. 555. 
Sewertzoff, A.: Kiipffer Festschrift, Jena, 1899. p. 281. 
* Parker, W. K.: Phil. Trans, 1883, p. 129, pl. v. 
* During the passage of this Memoir through the press, Sewertzoff has announced details concerning the 
development of the skull in the Gecko (Ascahabotes fascicularis) which fully supports this conclusion (cf. Anat. 
Anz. Bot. xviii. p. 36, 1900), 
w 
