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On the Breeding Habits of Echinus miliaris, with a 

 Note on the Feeding Habits of Patella uu/gata. 



By 

 J. H. Orton, B.Sc, A.R.C.Sc. 



With One Figure in the Text. 



While on shore-collecting expeditions in this district it was frequently 

 observed that Echinus miliaris has the habit of associating together in 

 pairs, and sometimes in groups of more than two.* The association of 

 these pairs and groups is sometimes so intimate that it is not possible 

 to interpose even the blade of a penknife between the interlocking 

 spines of the urchins. In all cases observed except one, such pairs were 

 placed side by side, but in one particular case the apical region of one 

 individual was almost certainly placed adjacent to the apical portion of 

 the other. In all the collecting expeditionsf — made at various times of 

 the year between April and August — on which groups Were collected, 

 the total number of urchins of all sizes obtained amounts to about 710.. 

 Among this number were obtained 84 groups, which amount in all to 

 189 specimens. In the earlier part of the investigation a group was 

 taken as such if the members were merely fairly close together, but 

 afterwards only those specimens were recorded which were actually 

 touching one another in the manner described above. Out of the total 

 of 84 groups only 27 were actually recorded definitely as touching one 

 another, although some of the other groups may have been touching. 

 Of these 27 closely associated forms all the individuals were ripe except 

 3 small specimens belonging to two pairs which were recorded as having 

 an immature gonad. The remainder consisted of 19 pairs c? ?, 2 pairs 

 ??, 1 pair ($^, and 3 groups respectively (^??,t cJc^?, and c??c?c?. 

 These facts in themselves point to the conclusion that in E. tniliaris 



* In a few cases as many as from 13 to 21 individuals have been found close together 

 under one stone. 



t In the search for groups of these urchins I am nmch indebted to the laboratory 

 fisherman, William Searle, for tlie zeal and care with which lie helped in the collecting. 



+ In this grouj) the 9 associated with the male was almost certainly spent, although it 

 was difficult to make certain whether on the other hand it might be immature. Hence it 

 is not grouped with the definite pairs of male and female. 



