Prof. H. Karsten on the Vegetable Cell. 185 
24. Bulimus Walli, mihi. 
B. testa acuminato-elongata, gracili, minute umbilicata; anfractibus 
octo, minute transversim striatis; intense brunnea ; apertura parva; 
columella parum reflexa; labro simplici. 
Hab. Kalka, Rockhampton (W. S. Wall, jun.). 
Diam. 0°12, alt. 0°44 une. Mus. C. 
The same type of shell as B. Tuckeri. 
25. Bulimus Onslowi, mihi. 
B. testa subobtecte perforata, ovata, solidiuscula, striata, albescente 
vel pallide cornea fasciis crebris transversalibus rufescentibus ; 
spira conica, obtusa; sutura profunda ; anfractibus quatuor, parum 
convexis, striis plurimis semiregularibus spiralibus transversisque 
sculptis, ultimo ventroso, spiram duplo dimidioque superante ; 
apertura subverticali, angulato-ovali, intus pallide plumbea ; peri- 
stomate simplici, tenui; margine columellari albido, reflexo, basi 
adnato. 
Long. 0°85, diam. 0°60 unc. 
Hab. Dirk Hartog’s Island, Shark Bay, Western Australia (Onslow). 
Australian Museum. 
26. Bulimus Jacksonensis. 
B. testa ovato-conica, imperforata ; anfractibus quatuor, vix convexi- 
usculis, glabris, nitidis, ultimo duplo ceteros zequante; spira ob- 
tusa; sutura impressa; apertura ovata; labro simplici, corneo 
pellucidoque ; columella recta. 
Long. 0°14, diam. 0°05 une. 
Hab. Darling Point, Port Jackson (King &c.). 
XX.—Histological Researches on the Formation, Development, 
and Structure of the Vegetable Cell. By Prof. H. Karsten, 
[Concluded from p. 133. ] 
§ XI. 
Intercellular substance.—Cuticle.— Metamorphosis of the substance of the 
different membranes of a joint-cell, and their development independently 
of the operation of a primordial utricle-—Formation of layers by the 
cell-membrane.— Difference between a cell-membrane and a layer of cell- 
membrane.— Varieties and causes of the transformations of the originally 
structureless cell-membrane. — Untenability of the hypothesis of a 
primordial sac. 
THERE are two antagonistic hypotheses in histology, viz. that of 
endogenous cell-formation and that of cell-fission; but there is 
a general concurrence on this point—that the walls of existing 
cells may be thickened in layers. 
By this laminated thickening (of the true nature of which, 
however, very different conceptions are adopted) the adherents 
