108 Moll . 
MOLLUSCOIDEA. 
genus there are two different generations of nurses, the first of which 
produces three sorts of buds — (1) the abortive ones above mentioned, 
(2) lateral buds, which remain sterile, and (3) median, which give origin 
to the second generation of nurses ; this latter is provided with a ventral 
stolo, and produces buds which become sexual animals. He comes to the 
conclusion that in Doliolum the alternation of generations is complicated 
with heterogony, the generation which is produced sexually producing 
abortive buds of the other kind of generation, but, at the same time, 
two other sorts of buds, one of which, the median, again produces the 
sexual form; in Salpa, the alternation is quite simple ; in Pyrosoma and 
SynascidicB, the same individual produces sexually and by budding; the 
sexually produced individuals remain asexual, and again produce by 
budding tho first form (truo alternation), and the asexually produced 
iudividuals are equivalent to their parents. Arb. z. Inst. Wien, iv. 
pp. 201-298, 5 pis., also separately ; abstract in J. R. Micr. Soc. (2) ii. 
pp. 331 & 332. 
B. Ulianin opposes this view, stating that the so-called dorsal and 
ventral stolo does not produce any bud at all, but serves only for the 
temporary fixation cf the young animal ; that the pieces detached from 
the rosette-shaped organ do not perish, but become amoeboid, and fix 
themselves on another part of the parent animal ; and, finally, that there 
is only one generation of nurses, which comes directly from the egg, and 
is provided with the rosette-shaped organ, producing by gemmation seve- 
ral different forms of buds — (1) the so-called lateral buds or shoots, (2) the 
median shoot or so-called second generation of nurses, and (3) the sexual 
animals. He tries to explain this strange mode of gemmation phylogeueti- 
cally by comparison with the Synascidice and Pyrosoma. Zool. Anz. 1882, 
pp. 429-436 & 447-453, also in a separate paper in Russian (title supra ) 
with a plate ; abstract in Arch. Z. cxp6r. x. pis. liv.-lix. 
Doliolum dcnticiilatum (Q. & G ), muelleri (Krolin), and rarum, sp. n., = 
muelleri (Kefersteiu & Elders), Messina, sexual and asexual forms de- 
scribed and figured by Grobben, Arb. z. Inst. Wien, iv. (2) pp. 74-76, 
pis. i. figs. 1-6, ii. fig. 7, iii. figs. 14-18. 
Salpid/e. 
F. Todaro compares his former results as to the development of Sa lpa } 
Atti Acc. Rom. (3) iv. [1880], with those by Barrois and Salensky 
[Zool. Rec. 1881, Moll. p. 100], and adds some new observations support- 
ing his views. The follicle is divided into two communicating sacs, the 
ovaric and the embryonic, succeeding each other in development. Todaro 
has seen the entry of a single zoosperm into the egg, its transformation 
into a pronucleus, and its conjugation with the female pronucleus; he 
also describes the segmentation of the egg in Salpa pinnata into the 
Morula stage, and the entry and gradual disappearance of the small lecy- 
thical or nutritive cells between the blastomeres. The embryonal sac 
adheres to tho wall of the uterus, and the point of adhesion projects into 
the respiratory cavity, which is constituted by a dilated part of the em- 
bryonal sac, and a part of the wall of the uterus (decidua interna); after- 
