44 



THE AMEKICAN MONTHLY 



[March, 



quently masquerading as a species of 

 another genus. When a colony, 

 which I have never 

 seen composed of 

 more than four indi- 

 viduals, has been un- 

 der observation for a 

 short time, one of the 

 zooids suddenly, and 

 for no discoverable 

 reason, often droops 

 and hangs against 

 the foot-stalk like a 

 flower v^ithering on 

 its stem. A moment 

 later it begins a rapid 

 rotation on its longi- 

 tudinal axis, and, 

 having twisted itself 

 free, darts in an uncer- 

 tain, zig-zag course 

 Fig. 1.1. — Codosiga b a c k w a r d through 

 florea, n. sp. ^.j-^g ^atcr. I havc 



seen this occur only when the colony 

 is formed of tvs^o members. Occasion- 

 ally another method of parting com- 

 pany is adopted. The discontented 

 one visibly lengthens its special foot- 

 stalk until it is two or three times the 

 height of the body, and then twists 

 free. The part of this freshly-formed 

 pedicel left on the primary foot-stalk, 

 as well as that carried oft' by the mi- 

 grating animal, does not harden in the 

 water, but speedily becomes invisible, 

 in the former instance seeming to melt 

 away, in the latter to be absorbed. 



After a longer or shorter voyage 

 the traveller settles do\\m somew^here 

 and pi'oceeds to erect a pedicel of its 

 own, so that the preparation on the 

 stage soon shows many collar-bearing 

 monads suspended from the cover- 

 glass, lifting themselves from the slide, 

 or resting on the water-weed, each 

 new foot-stalk varying in length with 

 age, and bearing but one terminal 

 zooid. It is now a monosiga, only 

 needing to assume a method of repro- 

 duction by transverse fission to remain 

 a monosiga ; and the obsei-ver, unless 

 he has first become acquainted with a 

 normal colony, and has witnessed the 

 results of these curious antics, would 



be more than excusable for a wrong 

 classification of the little creatures. 

 Its reproductive division is, however, 

 longitudinal, as with all species of its 

 genus. 



The shape of the body during the 

 monosiga-phase does not conspicu- 

 ously vary from that of the mature 

 animals composing a colony. It is 

 shortly campanulate, the height, 4/077 

 to -g^yi^j-Q-inch, but little exceeding the 

 "width, the posterior pai't usually 

 evenly rounded, very seldom tapering 

 to the pedicel, and bearing on the an- 

 terior body-half a characteristic, equa- 

 torial groove or depression. In form 

 it is somevi^hat changeable. As a mo- 

 nosiga, the part immediately beneath 

 the insertion of the collar expands, 

 the opposite extremity contracts, and 

 the creature then presents an appear- 

 ance amusingly like the corolla of a 

 monopetalous flow^er. As a codosiga 

 the bodies at the insertion of the foot- 

 stalk at times somewhat tapers, and 

 the internal or opposing surfaces be- 

 come flattened, thus giving the ex- 

 terior lateral outline a somewhat 

 gibbous contour. 



The depression surrounding the 

 body is permanent. When the ani- 

 mal is killed with picro-carmine it 

 sometimes expands greatly in front 

 and to the rear of this groove, so that 

 the dead body becomes fiddle-shaped. 

 This change I have not obsen-ed to 

 take place after using other chemicals, 

 and not always with picro-carmine. 

 The slender pedicel of course varies 

 in length w^ith the maturity of the 

 creature it supports. When of age, 

 or often w^hen the zooids part com- 

 pany, each to assume the monosiga 

 phase, the pedicel is usually from six 

 to eight times the height of the body. 

 Instances do rarely occur when the 

 body of a single animal is only one- 

 fourteenth the height of the foot-stalk ; 

 the little zooid having apparently 

 spent its substance in the formation 

 of a stem that shall over-top all its 

 competitors. Similar occurences are 

 not so uncommon among individuals 

 of the genus Homo. 



