328 SUMMARY OF CURRENT RESEARCHES RELATING TO 



practically no adaptive larval characters, and a considerable development 

 of adult characters. This is evidently correlated with the omission of 

 the free-swimming stage of the life-history. The excretory system 

 consists of a simple club-shaped bladder, a series of collecting tubes, and 

 «ixty-four flame cells, with their capillaries arranged in eight groups of 

 four on each side. J. A. T. 



Adaptability of Schistosome Larvae to New Hosts. — W. W. Cort 

 {Journ. Parasitology^ 1918, 4, 171-;^). In many cases, e.g. Fasciola 

 hepatica, the larvae of Trematodes can flourish in species which are not 

 their normal specific hosts. The larvae of Schistosoma hsematobium are 

 known from BulUnus contortus, B. di/botvski, Physopsis africana ; the 

 larvae of Schistosoma mansoni is known from Planorhis boissyi and 

 P. guadelupensis. Other examples are given of lack of specificity in 

 the choice of intermediate host. Thus among fork-tailed Cercarige 

 Cercaria douthitti Cort from Lymneea reflexa has been found in L. 

 stagnalis oppressa, L. stagnalis perampla, and Physa ancillaria parkeri ; 

 and an undescribed species from Douglas Lake was found in three 

 genera — Planorlis trivolvis^ Lymnsea exilis, and Physa ancillaria. The 

 question of the adaptability of the schistosomes to new interniediate 

 hosts becomes a problem of great significance in relation to the spread 

 of schistosomiasis. J. A. T. 



Bryozoa. 



New Japanese Polyzoa. — Yaichiro Okada {Annot. Zool. Japon., 

 1920, 9, 618-34, 1 pi., 7 figs.). A report on thirteen (five new) species 

 of Retepora (including Reteporellci) and two species of Adeonella, with 

 figures of the minute structure of zocecia, operculum, and the 

 ^' mandibles " of the avicularia. J. A. T. 



Echinoderma. 



Double Hydrocoele in Sea-urchin Larvae. — E. W. MacBride (Rep. 

 British Assoc, 1919, 87, 207-<s). When plutei of Echinus miliaris are 

 transferred at an age of three days to sea- water, the salinity of which 

 has been increased by adding 2 grm. of NaCl per litre, left there for a 

 week, and then re-transferred to ordinary sea-water, they show at the 

 age of about twenty-one days in a certain percentage of cases (not more 

 than 5 p.c.) two hydrocoeles. It is suggested that the exposure to 

 hypertonic water acts on a hidden rudiment in the larva and starts tlie 

 right hydrocoele developing. It has been previously shown by the 

 author that the organs developing on one side of the larva tend to 

 inhibit the development of similar organs on the other side. So, when 

 the proper hydrocoele on the left side begins developing and gets a 

 long start over its right antimere, it may check and eventually entirely 

 suppress the development of this. The re-transference to normal sea- 

 water may possibly hold up temporarily the exuberance of development 

 of the left side and allow the right side -to hold its own. "If this 

 supposition be 'well founded, echinoderm development would afford a 

 striking instance of that ' struggle between the parts ' on which Roux 

 has always insisted as an important feature in development." J. A. T. 



