16 Dr. F. Miiller on the Development of the Stomapoda. 



of three at the extremity of the last fourteen joints of the shorter, 

 42-jointed branch. In the Decapoda they appear usually to 

 occupy the commencement of the flagellum, leaving the extre- 

 mity free. This is the case in Mysis, in one species of which 

 (fig. 10) they are condensed upon a peculiar process. So also 

 in Crabs, Porcellance, and Paguri (fig. 8), in which they occur 

 in the greatest number and of the largest size (up to 1 mill, in 

 length), and, forming one or more transverse rows, beset the 

 thick short joints of the branch, which rapidly diminishes from 

 its thickened base. When the anterior antennse serve as feet, 

 the bacilli are wanting, as in the larvse of Prawns * ; or they 

 spring from the body itself, as in the larvse of Balani and E-hizo- 

 cephala. 



The bacilli are generally simply cylindrical; I found them 

 dilated into a bulbous form at the base, and here furnished with 

 a tougher membrane, in Squilla (fig. 11), in a small Prawn 

 {Hip'polyte ? fig. 9), and in Ocypoda. The extremity is usually 

 rounded off in a hemispherical form, and sometimes exhibits a 

 small strongly refractive spot. In the Prawn just mentioned 

 (fig. 9 a) a short delicate point was appended to the rounded 

 extremity. Sometimes they are narrowed towards the extremity : 

 I found them thus in Pagurus ; here, as in the Crabs and 

 Porcellance, they are divided by delicate annular furrows into 

 shorter or longer segments, and conically pointed. In the larger 

 bacilli the contents sometimes appear delicately striated longi- 

 tudinally, or very fine granules arranged in longitudinal rows 

 are seen in them. 



What is the function of these bacilligerous flagella ? If we 

 are unwilling to assume a sense entirely deficient in us inhabit- 

 ants of the land (in favour of which, however, the rudimentary 

 condition of the inner antennse in terrestrial Crustacea, such as 

 Onisci, Orchestia, and Ocypoda f, might be adduced), we can 

 scarcely avoid considering them as organs of smell. In the 

 Crabs, in which their bacilli are most highly developed, they are 

 unadapted for feeling solid bodies, on account of their position, 

 their inconsiderable length, and even on account of their bearing 

 these delicate and readily injured appendages. From perceiving 

 movements in the water, for which they would appear to be but 

 ill adapted even on account of their shortness, they are prevented 

 by a rapid current passing by and over them from the mouth. 

 In a current of this kind, running from the mouth, we should 

 certainly not seek for organs of taste. Thus, of our five senses, 



* The antennae of the Prawns are metamorphosed swimming-feet ; the 

 swimming-feet of the Daphnice are, however, hardly "transformed an- 

 tennse." 



t In Gelasimus, also, I find the bacilli unusually delicate and short. 



