ON PHORONIS OVA MS, STRKTHILL WRIGHT. 
121 
•eggs and developing embryos, a great number of larvas being 
set free from time to time. At the end of this season the 
lophophores are lost and the colonies then consist of blackish 
u cakes” of matted tubes, from 1 to 2J cm. in thickness. 
At the recommencement of the favourable season these 
eakes become covered by a une riche vegetation de Phoronis.” 
The tubes, examined during the “ mauvaise saison,” were 
found to contain remains of the body of the Phoronis, with 
lophophores in all stages of regeneration. Actinotrocha is 
said to occur rarely in the plankton at Naples at any time in 
the year, and Cerfontaine points out that it is difficult to 
suppose that the innumerable Phoronis which appear on 
the surface of the old cakes in a few days, at the commence- 
ment of the favourable season, can have been derived from 
larvas. He concludes, therefore, that P. kowalevskyi 
possesses a mode of spontaneous annual regeneration. 
A more detailed account of the process of regeneration is 
given by Schultz (1903 1 ), who describes the spontaneous loss 
of the lophophore in P. m tiller i at Heligoland, and compares 
it with the loss of the calyces in the Polyzoa Pedicellina 
and Urnatella, or of certain parts in Compound Ascidians 
(Diplosomidae) and Hydroids. He states that the process 
occurs, in Phoronis, whenever the conditions become 
unfavourable ; and that it is followed by the regeneration of 
the lophophore as soon as better conditions return. The loss 
of parts of the body under unfavourable conditions is 
regarded as a physiological necessity which has become a 
normal process in various animals and plants (as in the loss of 
leaves by deciduous trees) ; this iC reduction ” being explained 
as the loss of parts which can be dispensed with temporarily 
during a period of hunger, thus leaving fewer structures to 
be nourished during times when nutriment is not abundant. 
Schultz points out that a reduction-process of this nature, in 
an animal which has a high capacity for regeneration, may 
lead to transverse fission, “ and so indirectly to budding,” 
although he does not prove that an asexual method of repro- 
duction occurs in Phoronis. 
