ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
465 
(1) The primitive form of metagenesis of the Tunicata is to be 
found in those species of Synascidians which are capable of multiplying 
asexually in the larval stage. 
(2) Distaplia alone of the Synascidians exhibits an alternation of 
generation, while the development of the Didemniidae has no relation to 
that process. 
(3) The primordial bud of the Distaplia-laYva, is to be regarded as 
an intermediate stage between the simple bud and the stolo prolifer of 
the metagene tic Tunicata. 
(4) The stolo prolifer is derived from the bud which began to divide 
before separation from the mother-body. 
(5) In the oldest metagenetic forms the cc nurse ” died after the 
production of the sexual generation; in the course of metagenesis the 
length of the “ nurse’s ” life increased. In this connection Doliolum 
represents an intermediate stage between the Synascidiac and the 
Salpidae. 
Deglutition in Synascidiae.* — M. S. Jourdain, from observations on 
living specimens of Clavelina and PeropJiora , comes to the conclusion 
that one of the functions of the vibratile pit is the secretion of mucus ; 
by the aid of this the food particles are agglutinated into a cord, which 
is conveyed by the ciliated branchial band into the stomach. 
Nervous System in Embryos of Distaplia.j — Prof. W. Salensky 
has investigated the nature and development of the nervous system in 
embryos and larvae of Distaplia magnilarva. The larval nervous system 
consists of a somewhat complex cerebral vesicle, a trunk portion, and a 
tail portion. The cerebral vesicle is a vesicular tube, opening an- 
teriorly into the oral cavity, continued posteriorly into the trunk region, 
and expanded medianly into a sensory vesicle. This sensory vesicle 
lies between what may be called the Trichterblase and the Ganglionblase. 
In young embryos the anterior end of the funnel-vesicle is blind ; it is 
at first in a line with the rest of the brain, but is subsequently shunted 
to the left side. In connection with the sensory vesicle, the author 
describes the eye and the auditory organ. All the parts of the sensory 
vesicle, viz. retina, lens, pigment layer, and otolith cell, arise from the 
differentiation of one and the same epithelial layer of the primitive 
cerebral vesicle. The ganglion-vesicle lies between the choroid fold 
and the trunk region. Its lower wall is anatomically and genetically 
connected with the posterior part of the cerebral ganglion ; indeed the 
latter arises from a thickening of the inferior wall of the ganglion 
vesicle. The trunk region ( Bumpfmarlc ) connects the brain and the 
cord, and consists of an epithelial canal (part of the original neural 
canal) and of a well-developed layer of nerve-cells ( Bumpf-ganglion ) 
which has its origin from the cells of the posterior wall of the sensory 
vesicle. This Bumpf-ganglion is perhaps to be regarded as a great 
reflex centre for the larva, which through the cerebral ganglion conveys 
the results of sensory stimuli to the muscles. The degeneration of the 
cord during embryonic life is briefly referred to. After comparing in 
detail the nervous system of this larval Ascidian with that of other 
* Bull. Soc. Philomath., iv. (1892) pp. 35 and 6. See Ann. and Mag. Nat. Hist., 
x. (1892) pp. 482 and 3. f Morphol. Jahrb., xs. (1893) pp. 48-74 (2 pis.). 
