446 F. W. GAMBLE. 



that of (53) pi. xi, fig. 15, the sides flexed veutrally, almost 

 touching one another except in front, where they diverge. 

 The hinder end is produced into a finely-pointed tail. The 

 anterior end is truncate, the angles being frequently more or 

 less produced. It is a most actively sensitive animal, especially 

 during creeping movements, when the " head " is converted 

 into a funnel-shaped structure which explores the sur- 

 roundings. 



The general colour varies from greenish-brow^n to a warm 

 chestnut-brown, which is the usual tint. The anterior margin 

 is paler than the rest. The brown pigment is deposited in 

 the cell of a " symbiotic alga,^^ the nature of which has not 

 been thoroughly investigated. Transverse, narrow white bars, 

 1 — 2 in number (v. Graff has observed three, and Claparede 

 [35, pi. vi, fig. 2] figures four such bands), are present in large 

 individuals (1-75 mm. and upwards). They are the expression 

 of a large number of very small irregular granules, insoluble 

 in acids (v. Graff). Claparede has suggested that these bars 

 may be a '' caractere senile." This view is supported by 

 V. Graff, since he finds that the bars become more and more 

 distinct with the increased size and age of the animal. The 

 epidermis contains flagella, rhabdites, and pigment. 

 The latter forms elongate masses of rod-like granules. The 

 mouth, which is ventral and subcentral, leads into a very 

 short pharynx. The eyes are constantly present in this 

 species. They are red pigmented bodies, and occur right and 

 left of the otolith. Poison-organs (''Gift-Organe") have 

 been discovered by v. Graff (44) in this and other species of 

 Convoluta (C. groelandica, cinerea, flavibacillum, bi- 

 maculata). They consist in C. paradoxa of a pair of pyri- 

 form, transparent, muscular vesicles, provided with hollow 

 chitinous tips, and are placed at the margin of the body in 

 such a way that when this is flexed ventrally the tips are 

 directed towards the mouth. The contents consist of small 

 refractive granules. At each contraction of the muscular 

 wall the tip is moved forwards, at the same time dis- 

 charging some of its contents. This oral pair of poison- 



