Recent Observations on Neck Extensions in Folliculinids (Protozoa) 1 
Donald C. Matthews 
Despite species variations, the process of follic- 
ulinid lorica formation is fundamentally similar 
(Penard, 1919; Andrews, 1923; Faure-Fremiet, 
1932; Dewey, 1939; and Das, 1947). In all a 
motile, nonfeeding stage becomes attached, se- 
cretes a sac and neckband gradually metamor- 
phoses into a sessile feeding stage characterized 
by peristomal lobes. 
Although in certain well-established colonies 
restrictive attachment areas may modify sac 
length, breadth, and height, modifications in 
neck length and number of spiral whorls seem 
not to be thus affected (Matthews, 1963). De- 
spite the fact that certain folliculinids with 
poorly developed necks ( Ascohius simplex and 
Folliculina boltoni ) seem not adversely affected, 
nevertheless it is commonly assumed that well- 
developed necks and neck extensions afford 
some survival value; i.e., the entrance of preda- 
tors and detritus is lessened. Although this is 
an engaging conjecture, actually long necks and 
neck extensions afford little advantage. Rather, 
such folliculinids, responding to current disturb- 
ance, contract their peristomal lobes, whereas 
short-neck forms, not so affected, continue to 
feed. Since our knowledge of folliculinids is 
too meager to warrant conclusions as to why 
extensions are made, our attention for the pres- 
ent might best be focused on the stage (or 
stages) of the life-cycle responsible for their 
formation. The purpose of this paper is to 
place in question the limited alternatives of 
existing theories, and to rekindle interest in a 
question unsolved since 1923. 
As previously stated, on completion of a 
lorica a nonfeeding swimmer usually meta- 
morphoses into a feeding sessile organism char- 
acterized by peristomal lobes. It is generally 
1 Department of Zoology, University of Hawaii. 
Contribution No. 204. Hawaii Marine Laboratory, 
University of Hawaii, Honolulu 14, Hawaii. Manu- 
script received May 31, 1962. 
assumed that, in nature, this organism respon- 
sible for the lorica remains for some time its 
occupant. However, once the terminal lip is 
completed, a disturbed organism may sever its 
body-attachment point and, without developing 
peristomal lobes or actually living in its lorica, 
may vacate it and subsequently begin the process 
anew. 
Usually, however, on completion of the term- 
inal lip the organism withdraws into its sac 
and, following a rest period, metamorphoses 
into a sessile feeding stage. Under laboratory 
conditions, this stage may last from one to 
several days. This period is followed by one of 
two possible courses: either metamorphosis re- 
sults in a motile stage which vacates the original 
lorica; or, following binary fission, a distal 
portion metamorphoses into a motile stage 
whereas a proximal portion metamorphoses into 
a sessile stage which, for some time, occupies 
the original lorica. 
Thus, subsequent neck extensions might be 
the result of ( 1 ) the stage that secreted the 
original lorica, (2) the stage remaining in the 
original lorica following binary fission, ( 3 ) the 
stage leaving the original lorica following binary 
fission, or (4) a "new” swimmer (or swimmers) 
entering another lorica. Although most investi- 
gators agree on the general process of lorica 
formation, few agree on the stage of the life 
cycle responsible for neck extensions. And, de- 
spite the above possibilities, the formation of 
neck extensions is today explained in the light 
of limited alternatives: either they are the 
result of the sessile stage which secreted the 
original lorica, or they are the result of a "new” 
swimmer which enters an empty lorica. 
In a personal communication E, A. Andrews 
(1952) states: 
No one has seen extensions actually in the 
process of making, but Hadzi [1951] gives 
some pages of argument that they are made 
229 
