784 CLASS V. AKACHNIDA. 



an anterior pore from which the blood flows when the heart 

 contracts. In Colossendeis there is no pericardium. Respiration 

 is cutaneous. 



The testes are two longitudinal tubes lying in the body and 

 connected posteriorly so as to be U-shaped. They . give off 

 segmentally arranged vasa deferentia which pass to open on 

 the tibial or fourth joint of either all the walking legs, or of three 

 pair, or of two. The ovaries are shaped primitively like the 

 testis, but in many forms the portion in the body atrophies and 

 the ova all arise from lateral portions which have grown into 

 the legs. The fertilization is external and the males carry off 

 the eggs on their ovigerous legs. The young are often hatched 

 with only the three anterior appendages. 



Dr. Hoek * divides the Pantopoda into four families : 



Fam. 1. Nymphonidae. In this family the mandibles and palpi are 

 well developed, the ovigerous legs present in both sexes and as a rule 

 they bear denticulated spines. The only genus is Nymphon with some 

 forty species. 



Fam. 2. Colossendeidae. Mandibles rudimentary or absent, well 

 developed palpi, and ovigerous legs in both sexes as a rule with denticulate 

 spines. This family is by far the largest in the number of genera it con- 

 tains, Ammothea, Bohrnia, Phanodemus, Phynchothorax, Pephredo, Platy- 

 chelus, Oiceobathes, Ascorhynchus, Zetes, Parazetes, Pariboea, Alcinous, 



Acheli a , Tanystylum, Lecithorhynchus, 

 Oorhynchus, Colossendeis, Pasithoe, Endeis, 

 Discoarachne, Barana, Clotenia, Trygaeus. 



Fam. 3. Pallenidae. Strongly developed, 

 chelate mandibles, palps rudimentary or 

 absent. Only three genera ; Pallene with 

 ovigerous legs in both sexes furnished with 

 denticulate scales ; and Phoxichilidium, some 

 species with ovigerous legs present in both 

 FIG 1-509. Pycnogonum Utorale, sexes but w i t } lout denticulate scales, in other 

 AB pair of legs used for carry- 

 ing the eggs. species the ovigerous legs are confined to 



the males ; Neopallene. 



Fam. 4. Phoxichilidae. Mandibles and palpi absent or rudimentary. 

 Hannonia has ovigerous legs in both sexes but no denticulate spines, 

 Phoxichilus and Pycnogonum have them only in the male. 



[ We have followed Dr. Hoek in this scheme of classification, but in Lan- 

 kester's article the Nymphonidae with the genus Nymphon and the Palleni- 

 dae with the genus Pallene are grouped together as the Nymphonomorpha. 

 The family Ascorhynchidae with the genera Ascorhynchus and Ammothea, 

 together with the family Colossendeidae with the genera Colossendeis and 

 Discoarachne, make up the group Ascorhynchomorpha ; whilst a third group, 

 the Pycnogonomorpha, comprise the family Hannoniidae with the genus 

 Hannonia and the Pycnogonidae with the genera Pycnogonum and 

 Phoxichilus. 



