186 
MOLLUSCOIDA. 
tract, the sexual organs, and the vascular system, and is called 
abdominal gem (Bauchknospe) . From the peduncle of the first 
come the oesophagus and the rectum. In Botryllus also the egg 
produces only one embryo and one individual. The supposed 
eight embryos in the egg are the first elements of the stolons, which 
augment afterwards in number, and persist in the compound 
colony. The other individuals of Botryllus arise from gems pro- 
duced by the first. This first individual is always without sexual 
organs, and produces, therefore, no eggs; the following indi- 
viduals, produced by gemmation, produce eggs. There are no 
preexisting orifices for the issue of the eggs ; but these force their 
way through the integument of the mother, taking a part of it 
with them as a temporary envelope. 
The first appearance and development of the medullary 
tube, the intestinal tract, the branchial sac and its fissures 
are the same in the compound and in the simple Ascidians; 
but several of Kowalewsky’s observations concerning this de- 
velopment of the embryo are erroneous. Z. wiss. Zool. xx. 
pp. 512-518. 
Botryllus schlosscri (Pall.), Gould, Invert. Mass. p. 3, pi. 23. fig. 319, Mas- 
sachusetts. 
POLYZOA. 
1 
K. B. Reichert thinks that in the Bryozoa neither true 
muscles nor true nerves exist, the histological structure of the 
organs hitherto regarded as such being different from that of the 
muscles and nerves of the higher animals\ consequently he pro- 
poses to remove the Bryozoa from the Molluscoida, and to place 
them near the Anthozoa and Medusae in a large division of lower 
evertebrate animals, which corresponds otherwise to LeuckarPs 
Ccelenterata. He regards the Bryozoa generally as subject to 
alternating generation — the so-called cell being a distinct pre- 
vious individual, to be compared with the nutrix of the other 
cases of alternating generation, the ^^collare setosum^^ (oper- 
culum) and ‘‘ collare stellatum belonging to the same, and the 
intestinal tractus, with the crown of tentacles, constituting a 
second individual, which takes its origin by gemmation from the 
first. He adopts for the first the name fostering capsule [Brut- 
kapsel)y for the second the name bryozoid. The whole organi- 
zation of the Bryozoa is interpreted according to this view ; and 
the invagination of the bryozoid within the cell by two sorts of 
retractores is the object of special research. Finally, the author 
distinguishes between those Bryozoa in which a distinct common 
stem exists, called bryozophylon, which bears the single animals 
on its sides, as in the Vesiculariadae, and those which are con- 
stituted only by the single animals budding one from the other, 
Avithout a common stem, as in most other Bryozoa. He calls 
