10 ANTARCTIC MARINE 



DESCRIPTIONS OF THE SPECIES 



CHARACTERS COMMON TO ALL THE SPECIES 



Disregarding Thoracostoma, which is exceptional in the large size 

 of the caudal glands, the possession of eye-spots, of distinct dermal pores 

 and of oesophageal glands, and also in the possession of relatively very 

 strong spicula with a compound framework, it may be said that the 

 following characters are common to all the species here described: 



There is no median oesophageal bulb, and no pre-rectum. The tail 

 is of approximately the same form in both sexes, and in all cases is sup- 

 plied with a rather simple spinneret, and with caudal glands the lat- 

 ter confined to the tail. The eggs, so far as known, are smooth and 

 comparatively thin-shelled, and are deposited before segmentation 

 begins. 



All known males have equal spicula of simple framework, and all 

 are without bursa. There are no eye-spots. The cuticle is colorless, 

 or nearly so, is without distinct pores, and is destitute of longitudinal 

 striae except obscure indications in Spilophora serrata and Chromadora 

 meridiana, where the secondary elements of the cuticle arrange them- 

 selves also to a certain extent in longitudinal lines. 



The renette, when present, has its cell behind the cardiac constriction, 

 except in Anticoma. Glands in the interior of the oesophagus have 

 been seen only in Thoracostoma, and possibly, though these latter are 

 of another character, in Monhystera frigida and polaris. The intestinal 

 granules give rise to a tessellation only in Anticoma and Laxus. The 

 spicula are arcuate, except in some Monhysteras; and cephalated except 

 in Anticoma, Terschellingia and Euchromadora antarctica. There are 

 no male papillae except in Anticoma and Monhystera antarctica. Male 

 supplementary organs occur only in Anticoma, Chromodora polaris, Eu- 

 chromadora antarctica, Aplectus, Thoracostoma, and in Spilophora ser- 

 rata and edentata. The musculature of the oesophagus is fine except in 

 Thoracostoma and Monhystera polaris, frigida and pilosa, though it is 

 somewhat coarse in the bulb of Laxus. 



If the reader will add these characters to those given under each 

 species heading, and will utilize in a similar way the common charac- 

 ters given in the keys and generic descriptions, he will find himself in 

 possession of a very detailed description of each species, covering a 

 number of new and interesting anatomical features. 



