Mr. C. Spence Bate on the Nidification of Crustacea. 165 



to the structure, somewhat resembling a pear. Many of the 

 nests were in what appeared to be an unfinished state. If so, 

 they were constructed bit by bit, commencing from the smaller 

 extremities, which were attached to the stems of the zoophyte. 

 One side appeared to be so closely built-in with that on which 

 it rested, as to render them very secure and strongly fixed. 



Another species of this same genus* has been sent to me by 

 Mr. Gosse from Ilfracombe and Tenby, together with the 

 abodes constructed by it. Those found at Ilfracombe were 

 attached to a leaf of green Ulva. They were chiefly gathered 

 about the roots of the plant, but some few were constructed 

 further up. The specimen from Tenby had the nests thickly 

 clustered around the base, and were gradually progressing up 

 the stem of an old Tubularia. 



These nests, when examined under the microscope, appear to 

 be composed of grains of fine mud cemented by some glutinous 

 material that the animal secretes. 



Mr. Alder kindly sent me a specimen that he had dredged ; it 

 consisted of small mud-tubes, about a quarter (or little more) of 

 an inch in length, four of which were slenderly attached, at one 

 extremity only, to a bit of Antennularia. Examination proved 

 them to contain a species oi Siphonocetus (PI. VIII. fig. 2). Un- 

 like Kroyer's species, the tubes of this were formed of mud, laid 

 on, layer after layer, in successive rings, giving a somewhat 

 annular appearance to the structure. 



We here perceive that it is a more or less permanent habit for 

 the species of several well-marked genera to build by their own 

 exertions abodes in which they dwell. It is only natural to 

 suppose that, having a common instinct, however varied their 

 general form may be, they must in some parts of their struc- 

 ture possess some features common to the whole. It is upon 

 the force of this argument that this group is separated from 

 others to which in their general form they ofier a striking resem- 

 blance. Upon the importance of these characters respectively 

 rests the strength of the subfamily Podocerides in a natural clas- 

 sification, as distinct from Corophiides ; for no philosophic natu- 

 ralist could allow a group to be made if the habit were the only 

 resemblance between species, since an apparent eccentricity (of 

 which this class affords abundant examples) must disturb the 

 arrangement. 



Without examining the whole of the generic characters, we 

 shall, I think, be able to exhibit certain well-marked resemblances 



* I am inclined to think it is an undescribed species : it more nearly re- 

 sembles Podocerus {Cerapus) fucicola of Stimpson than either of the other 

 species. 



