270 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Protoplasmic Connections between Blastomeres.* * * § — Prof. J. A. 
Hammar finds that blastomeres are, in many cases, not quite isolated 
from one another, but are connected more or less definitely by proto- 
plasmic bridges. He finds this in Coelentera ( Cyanea cajpillata , Aurelia 
aurita , Actinoloba dianthus) ; in Worms ( Pomatoceros triqueter , Prosllie- 
cerseus vittatus , Malacobdella grossa ) ; in Echinoderms ; in Molluscs 
(JEolis papillosa) ; in Tunicata (Clavelina lepadif ormis, Ciona intestinalis) ; 
and in other cases. 
Mesoderm and Body-Cavities. t — Dr. T. H. Montgomery, jr., com- 
ments upon the multifarious development of the mesoderm. It may 
arise from the ectoderm, from the endoderm, or from both ; it may arise 
from the endoderm by multipolar delamination, by unipolar delamina- 
tion, or in the form of epithelial diverticula ; its origin is further com- 
plicated in meroblastic ova. Moreover, mesoderm and mesenchyme 
are but extremes of a series. 
As to the cavity enclosed by the mesoderm, it may be derived from 
archicoel or from gastrocoel; and it is interesting to inquire where a 
morphological distinction can be drawn between, for instance, the 
archicoelic coelome of an Annelid and the gastrocoelic coelome of a 
lancelet. The author discusses such questions, and concludes that 
particular differentiations of body-cavity cannot be safely homologised 
with similarly situated cavities in other groups. Hot even apparent 
similarity of development can be relied on ; for the early development 
and differentiation of the cavities must be referred, directly or indirectly, 
to the modes of cleavage and gastrulation, which often differ widely in 
closely allied forms. Indeed, before seeking to homologise the body- 
cavity, the morphological value of the organs and their mutual topo- 
graphy must first be determined. 
Epitrichium of the Chick.t — Herr B. Rosenstadt, in his studies on 
cornification, has been led to investigate tbe epitrichium of the chick, 
i.e. those cells on bill, scales, &c., in which both nucleus and cytoplasm 
are subject to kerato-hyaline degeneration. He concludes that the 
epitrichium represents a phylogonetically primitive state, a Vorstufe 
of the stratum corneum, just as keratohyalin may be said to bear the 
same relation to horn. In Mammals also this phylogenetic survival 
may recur ; but the formation of horn is entirely independent of that 
of keratohyalin. 
b. Histology. 
Relation between the Form and the Metabolism of the Cell.§ 
Dr. M. Verworn gives illustrations from Protozoa, &c., to show the 
dependence of cell-form on its chemical relations with the surrounding 
medium. Thus it is well known that with the withdrawal of oxygen 
the formation of pseudopodia ceases, and many other cases are familiar. 
Cell-Boundaries. || — Prof. Ch. van Bambeke discusses the question of 
cell-boundaries in animals, and the meaning of the term cell-membrane. 
* Arch. f. Mikr. Anat., xlix. (1897) pp. 92-102 (1 pi.), 
t Journ. Morphol., xii. (1897) pp. 355-66. 
j Arch. f. Mikr. Anat., xlix. (1897) pp. 561-85 (1 pi.). 
§ Sci. Progr., April 1897, pp. 370-78 (1 fig.). 
|| Bull. Soc. Beige de Microscopie, xxiii. (1897) pp. 72-87. 
