308 OLIGOCHAETA 



Definition. Length, 2-5 mm. Oesophagus an long as pharynx. Blood-vessels quite normal. 

 Hah. — Europe. 

 Vbjdovsky thinks that d'Udekem's Gh. mulleri (which the latter ought to have 

 called ' vermicularis ' — as he puts this name down as the only synonym) is identical 

 with Ch. diastropha. It is to be distinguished, according to d'Udekem, from 

 Oh. limnaei only hy fewer setae and absence of 'spicules ^pidermiques.' These 

 latter processes ( = tactile hairs) are figured by Vejdovsky in Ch. diastrophus, so the 

 identification is less certain. Vaillant believes (p. 450) that d'Udekem's Ck. mulleri 

 is Gh. diaphanus j the difierence in size may be, he thinks, a matter of age ; but 

 this does not seem likely, the difference being too great. Vejdovsky figures (24, PI. vi, 

 fig. I a, chp) a small chitinous plate upon hinder median aspect of brain, the nature 

 of which is mysterious. 



J 



Family ENCHYTRAEIDAE. 



Defiwitioh'. Setae (absent in Anaehaeta) short, straight, or curved, not bifid at 

 extremity. A single pair of ealciferous glands sometimes present. Dorsal 

 blood-vessel only present anteriorly, sometimes with, cardiac body. Testes 

 in XI, male pores on XII ; a reduced spermiducal gland present ; oviducts 

 represented by pores. Spermathecae, one pair ^ in V generally opening into 

 gut, with or without diverticula. Dorsal pores occasionally present. 



This family of Oligochaeta is very numerous in species, which are all of small 

 size, ranging from a length of 3 mm. to 40 mm. The structure of the Enchytraeidae 

 has been mainly elucidated by Vejdovsky (3, 20), ErsEN (13), and Michaelsen 

 (1-5, 16) ; to a less degree by d'Udekem (3), Clapaebde (3), and Ude (1, 2). 

 Michaelsen has recently published a detailed ' Synopsis ' of the family, the conclu- 

 sions set forth in which are, in the main, adopted here. The family is a very 

 natural one ; there appear to be no forms transitional between the group and other 

 Oligochaeta. This is satisfactory to the systematist, but it renders the labours of 

 the naturalist who desires to study the inter-relationships of the different groups 

 of Oligochaeta extremely difficult. 



All the Enchytraeidae have a prostomium ; in most there is a single pore upon 

 the prostomium; in a few forms (e.g. in Fridericia galha) there are also dorsal 



' Henlea puteana with two pairs is the only exception. 



