182 OLIGOCHAETA 



species selected was the large Aeolosoma fenebrarum. The most interesting fact 

 in this process is the entire absence of the formation of any budding zone such as 

 exists in the Naidomorpha (see below). In Aeolosoma there is simply a division 

 of the parent organism into two ; the formation of the head of the newly-formed 

 individual is ushered in by a dorsal thickening, which is the basis of the brain ; 

 the next event is the increase of the future head of the daughter zooid and the 

 appearance of muscular strands. Very soon there appear a pair of provisional 

 nephridia, such as seem alwaj r s to occur in the head of the lower Oligochaeta when 

 produced in this asexual way. It is important to observe that the pharynx is a new 

 structure invaginated from the epidermis, and not produced by any modification 

 of the existing section of the gut. This formation of the pharynx was also found 

 to occur in Aeolosoma variegatum (see VEJDOVSKY 18). 



Species of AEOLOSOMA. The division of the genus into species is a matter 

 of no little difficulty, on account of the very imperfect descriptions which the older 

 authors have given. Only six species can be at present regarded as well established ; 

 four of these, viz. A. hemprichii, A. quaternarium, A. tenebrarum, and A. variegatum, 

 have been clearly discriminated by VEJDOVSKY (18 and 24) one, A. niveum, by 

 LEYDIG (4) ; the remaining species, A. headleyi, I have described myself (68), and 

 believe to be distinct from any of the above. The following is a complete list of 

 all the species which may possibly be regarded as distinct. 



(1) Aeolosoma hemprichii, EHRE.NBERC;. (6) Aeolosoma headleyi, BEDDARD. 



(2) quaternarium, EHRENBEKG. (7) ., niveum, LEYDIG. 



(3) ., variegatum, VEJDOVSKY. (8) leidyi, CRAGIN. 



(4) aurigena, EICHWALD. (9) ternarium, SCHMARDA. 



(5) tenebrarum, VEJDOVSKY. (10) macrogaster, SCHMARDA. 



The following species are somewhat uncertain in position and affinities. 



Two of the species described by SCHMARDA, viz. Aeolosoma, ternarium and A. maavgaster, 

 have been referred by VAILLANT to a distinct genus, Pleurophlebs, on account of (i) absence of 

 coloured globules in the skin, (2) the presence of two lateral blood-vessels. These two species 

 appear likely to prove very interesting, but their structure requires, in my opinion, a re-examination 

 before they can be admitted. 



Aeolosoma pictum of SCHMARDA (from New Granada) has red oil-globules and a spiral intestine ; 

 it is very doubtfully distinct from one or other of the red-coloured species, A. quaternarium or 

 A. hemprichii. 



Aeolosoma chlorostidum of WOOD MASON is only known by a name ; he referred to it inci- 

 dentally in describing an infusorian parasite. 



VOELTZKOW has recorded from Madagascar an Aeolosnma with 'golden -yellow' oil-drops, but 

 no further information is given. 



