334 SECTIONAL TRANSACTIONS.— C, D. 



September 15. — Mount St. Michael (by kind permission of Lord St. Levan), 

 Penlee Quay. The Royal C4eological Society of Cornwall invited the visitors to lunch 

 in Penzance. 



September 16. — South Terrass Mine. Messrs. Loverings, Ltd., entertained the 

 members to lunch and conducted the excursion over their china-stone and china-clay 

 properties. 



September 17. — Tremorebridge Quay. Very unfavourable weather caused the 

 abandoning of the day's programme at noon. 



SECTION D.— ZOOLOGY. 



Thursday, September 4. 



Presidential Address by Dr. W. T. Calman, F.R.S., on The Taxonomic 



Outlook in Zoology. (See p. 82.) 



Miss S. M. Manton. — Anaspides and Paranaspides.^^ 



The Habits and Feeding Mechanisms of Paranaspides and Anaspides. — Anaspides 

 is plentiful on Mount Wellington, Tasmania, but Paranaspides, formerly abundant in 

 the Great Lake, Tasmania, is now very scarce, and may be approaching extinction. 



Paranaspides resembles the more primitive members of the Malacostraca, such as 

 most Mysids and Euphausids, in that it filters the water in which it swims, and so 

 obtains part of its food requirements. The filtratory mechanism consists of the 

 maxilla and adjacent mouth parts, and is operated much as is the maxillary com- 

 ponent of the filtratory mechanism of filter feeding Malacostraca. However, in 

 Paranaspides the maxillary filter functions alone, unaided by a stream of water from 

 the thorax. Paranaspides provides a living example of an animal with a type of filter 

 feeding mechanism which, as has already been suggested, probably preceded the 

 Hemimysis type. The movements of the thoracic exopodites is simpler than that of 

 other Malacostraca already investigated, with the possible exception of some of the 

 most primitive living Mysids. 



A naspides, found in mountain pools with flowing water, is predominantly a bottom 

 living form, walking or swimming over the substratum. In swimming and walking 

 the thorax and abdomen are used as a single functional region, and the pleopods and 

 thoracic exopodites beat in series. This is quite unusual for the Malacostraca. 

 Anaspides, although it possesses a maxillary filtering mechanism of the same type as 

 that of Paranaspides, does not filter the water in which it swims, the mouth parts 

 being then stationary. The maxillary filtering mechanism, however, plays an important 

 part in collecting particles scraped off large masses of food which would otherwise be 

 swept away by the flowing water without an effective method for their collection. 

 The use of the primitive filtering mechanism is neatly correlated with the conditions 

 of life of the animal, little morphological change being involved. 



Both Paranaspides and Anaspides sweep up algal slime off weeds and feed to a 

 variable extent on large food as does a Mysid. 



The persistence at the present day of Crustacea as unspecialised in habits as Para- 

 naspides and Anaspides is associated with their habitat. Paranaspides has been well 

 protected from predatory fish by weeds, and Anaspides has no competitors in its 

 mountain pools. Both forms appear incapable of meeting competition and are very 

 inefficient hunters of live prey or of food of any size. 



Paranaspides has almost disappeared as a result of the artificial raising of the level 

 of the Great Lake by about 32 feet for the purposes of water power, and the consequent 

 dying off of nearly all the old weeds in the lake. 



Prof. H. Graham Cannon. — On the Internal Anatomy of a Marine Ostracod, 

 Cypridina (Doloria) levis Skogsberg. 



Hitherto very little has been known with certainty about the internal anatomy of 

 Ostracods owing to the extreme difficulty of fixation. However, some material 



