236 



THE AMERICAN NATURALIST [Vol. LV 



tlie substance which causes this defensive odor have not 

 been determined. 



Another means of protection is self-mutilation, exem- 

 plitied by Discodoris fragilis, that according to Eliot, 

 1899, throws off part or the whole of its mantle edge. 

 Collingwood, 1868, also records this habit of self- 

 mutilation of a Doris. 



Embeyology 

 The Efj/hhodi/ {Nidosome) 

 Bergh, 1902, describing the egg-body of Melihe hu- 

 cephala says: 



The spawn forms a laroo lieap of a diameter of '^^ em., composed of 

 the inmmierabh^ windiiiiis of a dull yellow tube of a diameter 0.75 mm. 



From this description it is clear that this nidosome is 

 quite different from that of M. leonina; it seems, indeed, 

 strange that the egg-body of two closely related species 

 can differ so widely. The external features of M. bu- 

 cephala, according to Bergh 's description, are not much 

 different from those of M. leonifia. It may })e a (]uestion 

 whether the egg-body attributed to M. huccphnld, l)y 

 Ik^rgh, actually belongs to this species. 



The writer during the summer of 1914 foiuid scNcial 

 iiidosonies among the eel-grass, but it was not known to 

 wliicli ;iiiinial they belonged until Melihe leonina was 

 s.M'ii to l;iy the same kind in the aquarium of the labora- 

 tni-\ ( Ag<M-sborg, 1919). These nidosomes of transparent 

 iimeous, or gelatinous substniicc wci'c fuiiiicl-shaped, 

 when suspended in the water, with tli<' .ipcx .-ittached to 

 some solid object (Fig. .'^). The a\('r;iuv siant-lieight of 

 tliosc <M)tiical stnictufcs was T) cii., with a iM'riinefer of 



(h.f..(l hiic^. th.' capMih- K-uliat.-Il to th.' |.i'fiphrr> of 



